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Linux and Unix nload App: Monitor Network Traffic and Bandwidth Usage In Real Time

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<span style="color: #3d85c6; font-family: "verdana" , sans-serif; font-size: large;"><u>Linux and Unix nload App: Monitor Network Traffic and Bandwidth Usage In Real Time</u></span></h1>
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<span class="drop_cap" style="background-color: white; color: #111111; float: left; line-height: 1em; margin: 0px 0.15em 0px 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: "verdana" , sans-serif;"><span style="font-family: "georgia" , "times new roman" , serif;">I</span><span style="line-height: 27px;">f you want to monitor network throughput on the command line interface, use nload application. It is a console application which monitors network traffic and bandwidth usage in real time. It visualizes the in and outgoing traffic using two graphs and provides additional info like total amount of transferred data and min/max network usage.</span></span></span></div>
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<span style="font-family: "verdana" , sans-serif; font-size: large;">Install nload on a CentOS/RHEL/Red Hat/Fedora Linux</span></h2>
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<span style="font-family: "verdana" , sans-serif;">First, <a href="http://www.hackthesec.co.in/2016/01/centos-rhel-scientific-linux-6-enable.html" style="color: grey; margin: 0px; padding: 0px; word-wrap: break-word;">turn on EPEL repo on a CentOS or RHEL</a> based system. Type the following yum command to install nload:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;"># yum install nload</span></code></div>
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<span style="font-family: "verdana" , sans-serif; font-size: large;">Install nload on a Debian or Ubuntu Linux</span></h2>
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<span style="font-family: "verdana" , sans-serif;">Type the following apt-get command:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ sudo apt-get install nload</span></code></div>
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<span style="font-family: "verdana" , sans-serif; font-size: large;">Install nload on a FreeBSD system</span></h2>
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<span style="font-family: "verdana" , sans-serif;">To install the nload via port, type:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;"># cd /usr/ports/net/nload/ && make install clean</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Or add the package</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;"># pkg install net/nload</span></code></div>
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<span style="font-family: "verdana" , sans-serif; font-size: large;">Install nload on a OpenBSD system</span></h2>
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<span style="font-family: "verdana" , sans-serif;">Type the following command:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ sudo pkg_add -i nload</span></code></div>
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<span style="font-family: "verdana" , sans-serif; font-size: large;"><u>Install nload using a source code on a Unix-like systems</u></span></h2>
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<span style="font-family: "verdana" , sans-serif;">First, grab the source code using either wget command or curl command:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ cd /tmp<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />$ wget http://www.roland-riegel.de/nload/nload-0.7.4.tar.gz</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />To untar a tar file called nload-0.7.4.tar.gz, use tar command, enter:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ tar xvf nload-0.7.4.tar.gz</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Cd to the directory containing the nloads's source code using cd command:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ cd nload*</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />And type <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">./configure</kbd> to configure the package for your system:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ sh ./configure</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />OR</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ ./configure</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Running configure takes a while. Type make command to compile the nload:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ make</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Finally, type <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">make install</kbd> to install the nload programs and related files as root user:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ sudo make install</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />OR</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;"># make install</span></code></div>
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<span style="font-family: "verdana" , sans-serif; font-size: large;">How do I use nload to display the current network usage?</span></h2>
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<span style="font-family: "verdana" , sans-serif;"><span style="font-family: "georgia" , "times new roman" , serif;">The basic syntax is:</span><span style="background-color: #fafbfc; color: #666666;"> </span></span></div>
<pre class="bash" style="background-color: #fafbfc; clear: both; color: #666666; line-height: 27px; margin-bottom: 27px; overflow: auto; padding: 14px; tab-size: 4; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;"><span style="font-family: "georgia" , "times new roman" , serif;">nload
nload device
nload <span style="color: #7a0874; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">[</span>options<span style="color: #7a0874; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">]</span> device1 device2
 </span><span style="background-color: white; color: #111111;">Just type the following command:</span></span></pre>
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<code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ nload<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />$ nload eth0<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />$ nload em0 em2</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Sample outputs:</span></div>
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<span style="font-family: "verdana" , sans-serif;">Fig. 01: nload command in action</span></div>
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<span style="font-family: "verdana" , sans-serif; font-size: large;">Controlling nload app</span></h3>
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<span style="font-family: "verdana" , sans-serif;">Once nload command executed, it begins to monitor the network devices. You can control nload with the following key shortcuts:</span></div>
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<li style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: "verdana" , sans-serif;">You can switch between the devices by pressing the <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><strong style="margin: 0px; padding: 0px; word-wrap: break-word;">left</strong></kbd> and <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><strong style="margin: 0px; padding: 0px; word-wrap: break-word;">right</strong></kbd> arrow keys or<kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><strong style="margin: 0px; padding: 0px; word-wrap: break-word;">Enter/Tab<kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"></kbd></strong> key.</kbd></span></li>
<li style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: "verdana" , sans-serif;">Press <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><strong style="margin: 0px; padding: 0px; word-wrap: break-word;">F2</strong></kbd> to show the option window</span></li>
<li style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: "verdana" , sans-serif;">Press <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><strong style="margin: 0px; padding: 0px; word-wrap: break-word;">F5</strong></kbd> to save current settings to the user’s config file.</span></li>
<li style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: "verdana" , sans-serif;">Press <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><strong style="margin: 0px; padding: 0px; word-wrap: break-word;">F6</strong></kbd> reload settings from the config files.</span></li>
<li style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: "verdana" , sans-serif;">Press <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><strong style="margin: 0px; padding: 0px; word-wrap: break-word;">q</strong></kbd> or hit <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><strong style="margin: 0px; padding: 0px; word-wrap: break-word;">Ctrl+C</strong></kbd> to quit nload.</span></li>
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<span style="font-family: "verdana" , sans-serif; font-size: large;">Setting the refresh interval of the display</span></h3>
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<span style="font-family: "verdana" , sans-serif;">The default value of interval is 100 milliseconds to refresh interval of the display. In this example, change to 500 milliseconds:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ nload -t {interval_number_in_millisec}<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />$ nload -t 500</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Sample outputs:</span></div>
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<span style="font-family: "verdana" , sans-serif;">Animated gif 01 - nload command in action</span></div>
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<span style="font-family: "verdana" , sans-serif; font-size: large;">Setting the type of unit used for the display of traffic numbers</span></h3>
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<span style="font-family: "verdana" , sans-serif;">The syntax is:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: "verdana" , sans-serif;">$ nload -u h|H|b|B|k|K|m|M|g|G<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />$ nload -U h|H|b|B|k|K|m|M|g|G<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />$ nload -u h<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />$ nload -u G<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />$ nload -U G</span></code><span style="font-family: "verdana" , sans-serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Where,</span></div>
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<li style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: "verdana" , sans-serif;">The lower case <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">-u</kbd> option: h means human readable (auto), b Bit/s, k kBit/s, m MBit/s and g GBit/s. The upper case letters mean the corresponding units in Bytes (instead of Bits). The default is k.</span></li>
<li style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: "verdana" , sans-serif;">The upper case <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">-U</kbd> option is same as lower case <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">-u</kbd> option, but for an amount of data, e.g. Bit, kByte, GBit etc. (without "/s"). The default is M.</span></li>
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Linux and Unix nload App: Monitor Network Traffic and Bandwidth Usage In Real Time

Linux and Unix nload App: Monitor Network Traffic and Bandwidth Usage In Real Time I f you want to monitor network throughput on the c...

Finding a File Containing a Particular Text String In Linux Server

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<span style="color: #0b5394; font-family: Georgia, Times New Roman, serif; font-size: large;"><u>Finding a File Containing a Particular Text String In Linux Server</u></span><br />
<span style="font-family: Georgia, Times New Roman, serif;"><span style="background-color: white; color: #111111; line-height: 27px;">I have been using Linux for a while on my server and have a large collection of the text file everywhere. I'm interested in learning about searching a text string. Can you tell me - how do I find a file containing a particular text string on my Linux server?</span><br style="background-color: white; color: #111111; line-height: 27px; margin: 0px; padding: 0px; word-wrap: break-word;" /><span id="more-520" style="background-color: white; color: #111111; line-height: 27px; margin: 0px; padding: 0px; word-wrap: break-word;"></span><br style="background-color: white; color: #111111; line-height: 27px; margin: 0px; padding: 0px; word-wrap: break-word;" /><span style="background-color: white; color: #111111; line-height: 27px;">I have to admit that there are tens and thousands of text files on any Linux or Unix based server. Finding and locating those files can be done with the find command. Unfortunately find command cannot look inside a text file for a string.</span></span><br />
<span style="font-family: Georgia, Times New Roman, serif;"><span style="background-color: white; color: #111111; line-height: 27px;"><br /></span></span>
<span style="font-family: Georgia, Times New Roman, serif;"><span style="background-color: white; color: #111111; line-height: 27px;">You need to use the </span>grep command<span style="background-color: white; color: #111111; line-height: 27px;">. The grep command searches the given input FILEs for lines containing a match or a text string.</span></span><br />
<span style="background-color: white; color: #111111; line-height: 32px;"><span style="font-family: Georgia, Times New Roman, serif;"><br /></span></span>
<span style="background-color: white; color: #111111; line-height: 32px;"><span style="font-family: Georgia, Times New Roman, serif;">grep command syntax</span></span><br />
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<span style="font-family: Georgia, Times New Roman, serif;">The syntax is:</span></div>
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<kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: Georgia, Times New Roman, serif;">grep "<span style="color: #996633; margin: 0px; padding: 0px; word-wrap: break-word;">text string to search</span>” directory-path</span></kbd></div>
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<span style="font-family: Georgia, Times New Roman, serif;">OR</span></div>
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<kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: Georgia, Times New Roman, serif;">grep [option] "<span style="color: #996633; margin: 0px; padding: 0px; word-wrap: break-word;">text string to search</span>” directory-path</span></kbd></div>
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<span style="font-family: Georgia, Times New Roman, serif;">OR</span></div>
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<kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: Georgia, Times New Roman, serif;">grep -r "<span style="color: #996633; margin: 0px; padding: 0px; word-wrap: break-word;">text string to search</span>” directory-path</span></kbd></div>
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<span style="font-family: Georgia, Times New Roman, serif;">OR</span></div>
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<kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: Georgia, Times New Roman, serif;">grep -r -H "<span style="color: #996633; margin: 0px; padding: 0px; word-wrap: break-word;">text string to search</span>” directory-path</span></kbd></div>
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<span style="font-family: Georgia, Times New Roman, serif;">OR</span></div>
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<kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: Georgia, Times New Roman, serif;">egrep -R "<span style="color: #996633; margin: 0px; padding: 0px; word-wrap: break-word;">word-1|word-2</span>” directory-path</span></kbd></div>
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<span style="font-family: Georgia, Times New Roman, serif;">OR</span></div>
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<kbd style="margin: 0px; padding: 0px; word-wrap: break-word;"><span style="font-family: Georgia, Times New Roman, serif;">egrep -w -R "<span style="color: #996633; margin: 0px; padding: 0px; word-wrap: break-word;">word-1|word-2</span>” directory-path</span></kbd></div>
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<span style="font-family: Georgia, Times New Roman, serif; font-size: small;">Examples</span></h3>
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<span style="font-family: Georgia, Times New Roman, serif;">In this example, search for a string called 'redeem reward' in all text (*.txt) files located in /home/tom/ directory, use:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep "redeem reward" /home/tom/*.txt</span></code><span style="font-family: Georgia, Times New Roman, serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />OR</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep "redeem reward" ~/*.txt</span></code></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Task: Search all subdirectories recursively</span></h4>
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<span style="font-family: Georgia, Times New Roman, serif;">You can search for a text string all files under each directory, recursively with <span style="color: red; margin: 0px; padding: 0px; word-wrap: break-word;"><kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">-r</kbd></span> option:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep -r "redeem reward" /home/tom/</span></code><span style="font-family: Georgia, Times New Roman, serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />OR</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep -R "redeem reward" /home/tom/</span></code></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Task: Only display filenames</span></h4>
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<span style="font-family: Georgia, Times New Roman, serif;">By default, the grep command prints the matching lines. You can pass <span style="color: red; margin: 0px; padding: 0px; word-wrap: break-word;"><kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">-H</kbd></span> option to print the filename for each match:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep -H -r "redeem reward" /home/tom</span></code><span style="font-family: Georgia, Times New Roman, serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Sample outputs:</span></div>
<pre style="background-color: #fafbfc; clear: both; color: #666666; line-height: 27px; margin-bottom: 27px; overflow: auto; padding: 14px; tab-size: 4; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">filename.txt: redeem reward
foobar.txt: redeem reward
...</span></pre>
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<span style="font-family: Georgia, Times New Roman, serif;">To just display the filename use the cut command as follows:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep -H -R vivek /etc/* | cut -d: -f1</span></code><span style="font-family: Georgia, Times New Roman, serif;"><br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Sample outputs:</span></div>
<pre style="background-color: #fafbfc; clear: both; color: #666666; line-height: 27px; margin-bottom: 27px; overflow: auto; padding: 14px; tab-size: 4; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">filename.txt
foobar.txt
...</span></pre>
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<span style="font-family: Georgia, Times New Roman, serif;">Task: Suppress file names</span></h4>
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<span style="font-family: Georgia, Times New Roman, serif;">The grep command shows output on a separate line, and it is preceded by the name of the file in which it was found in the case of multiple files. You can pass the <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">-h</kbd> option to suppress inclusion of the file names in the output:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep -h -R 'main()' ~/projects/*.c</span></code></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Task: Display only words</span></h4>
<div style="background-color: white; color: #111111; line-height: 27px; margin-bottom: 27px; padding: 0px; word-wrap: break-word;">
<span style="font-family: Georgia, Times New Roman, serif;">You can select only those lines containing matches that form whole words using the <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">-w</kbd>option. In this example, search for word 'getMyData()' only in ~/projects/ dirctory:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep -w -R 'getMyData()' ~/projects/</span></code></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Task: Search for two or more words</span></h4>
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<span style="font-family: Georgia, Times New Roman, serif;">Use the egrep command as follows:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ egrep -w -R 'word1|word2' ~/projects/</span></code></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Task: Hide warning spam</span></h4>
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<span style="font-family: Georgia, Times New Roman, serif;">grep command generate error message as follows due to permission and other issues:</span></div>
<blockquote style="background-color: white; border-left-color: rgb(221, 221, 221); border-left-style: solid; border-left-width: 1px; color: #888888; line-height: 27px; margin: 0px 0px 27px 14px; padding: 0px 0px 0px 14px; word-wrap: break-word;">
<div style="margin-bottom: 27px; padding: 0px; word-wrap: break-word;">
<span style="font-family: Georgia, Times New Roman, serif;">No such file or directory<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />No such device or address<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />Permission denied</span></div>
</blockquote>
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<span style="font-family: Georgia, Times New Roman, serif;">To hide all errors or warning message spam generated by the grep command, append2>/dev/null to grep command. This will send and hide unwanted output to /dev/null device:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">$ grep -w -R 'getMyData()' ~/projects/ 2>/dev/null</span></code></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Task: Display matched text in color</span></h4>
<div style="background-color: white; color: #111111; line-height: 27px; margin-bottom: 27px; padding: 0px; word-wrap: break-word;">
<span style="font-family: Georgia, Times New Roman, serif;">Pass the <kbd style="margin: 0px; padding: 0px; word-wrap: break-word;">--color</kbd> option to the grep command display matched text/words in color on the terminal:</span></div>
<pre class="bash" style="background-color: #fafbfc; clear: both; color: #666666; line-height: 27px; margin-bottom: 27px; overflow: auto; padding: 14px; tab-size: 4; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;"> 
<span style="color: #c20cb9; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">grep</span> --color <span style="color: red; margin: 0px; padding: 0px; word-wrap: break-word;">'word'</span> <span style="color: #c20cb9; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">file</span>
<span style="color: #c20cb9; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">grep</span> --color -R <span style="color: red; margin: 0px; padding: 0px; word-wrap: break-word;">'word'</span> /path/to/<span style="color: #c20cb9; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">dir</span>
<span style="color: #c20cb9; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">grep</span> --color -R <span style="color: red; margin: 0px; padding: 0px; word-wrap: break-word;">"192.168.1.5"</span> /etc/
<span style="color: #c20cb9; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">grep</span> --color -R -h <span style="color: red; margin: 0px; padding: 0px; word-wrap: break-word;">"192.168.1.5"</span> /etc/
<span style="color: #c20cb9; font-weight: bold; margin: 0px; padding: 0px; word-wrap: break-word;">grep</span> --color -R -h <span style="color: red; margin: 0px; padding: 0px; word-wrap: break-word;">"192.168.1.5"</span> /etc/ <span style="color: black; margin: 0px; padding: 0px; word-wrap: break-word;">2</span>>/dev/null
 </span></pre>
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<span style="font-family: Georgia, Times New Roman, serif;">Sample outputs:</span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJg5Kvvh80_Os3Oy4MrXsIoelk8S3A9gqlrYwOfDXl26Ou76cgDwOUVpAyIvjFEWVFynBF-WSaoNi9T-Yek0CU5AfO5MtL1np2cQ3NZdyUhCArpvMa3XFxQyJrJ_Tyxhh8CyPd1uFe7yA/s1600/grep-color-hide-spam_www.hackthesec.co.in.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJg5Kvvh80_Os3Oy4MrXsIoelk8S3A9gqlrYwOfDXl26Ou76cgDwOUVpAyIvjFEWVFynBF-WSaoNi9T-Yek0CU5AfO5MtL1np2cQ3NZdyUhCArpvMa3XFxQyJrJ_Tyxhh8CyPd1uFe7yA/s1600/grep-color-hide-spam_www.hackthesec.co.in.png" /></a></div>
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<span style="font-family: Georgia, Times New Roman, serif;">Task: Ignore case</span></h4>
<div style="background-color: white; color: #111111; line-height: 27px; margin-bottom: 27px; padding: 0px; word-wrap: break-word;">
<span style="font-family: Georgia, Times New Roman, serif;">Our final example ignore case distinctions in both the search PATTERN and the input files:</span><code style="background-color: #fafbfc; border: 1px solid rgb(222, 222, 222); clear: both; color: #666666; display: block; line-height: 1em; margin: 0px; overflow: auto; padding: 21px; word-wrap: normal;"><span style="font-family: Georgia, Times New Roman, serif;">grep -i -R 'word' /path/to/dir<br style="margin: 0px; padding: 0px; word-wrap: break-word;" />grep -i -r 'income tax' ~/accounting/</span></code></div>
<span style="background-color: white; color: #111111; font-family: Arial, 'Helvetica Neue', Helvetica, sans-serif; font-size: 16px; line-height: 27px;"><br /></span></div>

Finding a File Containing a Particular Text String In Linux Server

Finding a File Containing a Particular Text String In Linux Server I have been using Linux for a while on my server and have a large colle...

Linux x86 - Egg-hunter (13 bytes)

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Linux x86 - Egg-hunter (13 bytes)</h1>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGE6nn50dtfRFdRwQcczj1ro78IJlC9qzqpcm-FkrrCrZAPR3Hd5rOZSrE1fH9OrRJ8CIuYlATMlBEuQYxxetKiwCv4l_1pcBgYuvw4bRtIYq6ZwaXQI2PybVABxpOnpM4ZDKZ0OXx40Y/s1600/egg-hunter_www.hackthesec.co.in.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGE6nn50dtfRFdRwQcczj1ro78IJlC9qzqpcm-FkrrCrZAPR3Hd5rOZSrE1fH9OrRJ8CIuYlATMlBEuQYxxetKiwCv4l_1pcBgYuvw4bRtIYq6ZwaXQI2PybVABxpOnpM4ZDKZ0OXx40Y/s1600/egg-hunter_www.hackthesec.co.in.PNG" /></a></div>
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<table class="exploit_list" style="background-color: rgb(239, 239, 239) !important; border-radius: 3px !important; border-spacing: 1px; border: 1px solid rgb(221, 221, 221) !important; box-sizing: border-box; color: #666666; font-family: 'Open Sans', sans-serif; font-size: 14px; line-height: 24px; margin-bottom: 10px; margin-top: 10px; padding: 1px !important; width: 666px;"><tbody style="box-sizing: border-box;">
<tr style="background-color: rgb(248, 248, 248) !important; box-sizing: border-box;"><td style="background: rgb(225, 225, 225); box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">EDB-ID:</strong> 39204</td><td style="background: rgb(225, 225, 225); box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">CVE:</strong> N/A</td><td style="background: rgb(225, 225, 225); box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">OSVDB-ID:</strong> N/A</td></tr>
<tr style="background-color: rgb(248, 248, 248) !important; box-sizing: border-box;"><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">EDB Verified:</strong> <span class="fa fa-times" style="-webkit-font-smoothing: antialiased; box-sizing: border-box; display: inline-block; font-family: FontAwesome; font-size: inherit; font-stretch: normal; line-height: 1; text-rendering: auto;"></span></td><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">Author:</strong> <a href="https://www.exploit-db.com/author/?a=8467" style="-webkit-transition-duration: 0.3s; -webkit-transition-property: background-color, box-shadow, border, color, opacity; background-color: transparent; box-sizing: border-box; color: #337ab7; outline: 0px; text-decoration: none; transition-duration: 0.3s; transition-property: background-color, box-shadow, border, color, opacity;">Dennis 'dhn' Herrmann</a></td><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">Published:</strong> 2016-01-08</td></tr>
<tr style="background-color: rgb(248, 248, 248) !important; box-sizing: border-box;"><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">Download Exploit:</strong> <a href="https://www.exploit-db.com/download/39204" style="-webkit-transition-duration: 0.3s; -webkit-transition-property: background-color, box-shadow, border, color, opacity; background-color: transparent; box-sizing: border-box; color: #337ab7; outline: 0px; text-decoration: none; transition-duration: 0.3s; transition-property: background-color, box-shadow, border, color, opacity;"><span class="fa fa-file-code-o" style="-webkit-font-smoothing: antialiased; box-sizing: border-box; display: inline-block; font-family: FontAwesome; font-size: inherit; font-stretch: normal; line-height: 1; text-rendering: auto;"></span> Source</a> </td><td colspan="2" style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">Download Vulnerable App:</strong> N/A</td></tr>
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Linux x86 - Egg-hunter (13 bytes)

Linux x86 - Egg-hunter (13 bytes) EDB-ID: 39204 CVE: N/A OSVDB-ID: N/A EDB Verified: Author: Dennis 'dhn' Herrman...

Linux/x86 execve "/bin/sh" - shellcode 24 byte

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Linux/x86 execve "/bin/sh" - shellcode 24 byte</h1>
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<table class="exploit_list" style="background-color: rgb(239, 239, 239) !important; border-radius: 3px !important; border-spacing: 1px; border: 1px solid rgb(221, 221, 221) !important; box-sizing: border-box; color: #666666; font-family: 'Open Sans', sans-serif; font-size: 14px; line-height: 24px; margin-bottom: 10px; margin-top: 10px; padding: 1px !important; width: 666px;"><tbody style="box-sizing: border-box;">
<tr style="background-color: rgb(248, 248, 248) !important; box-sizing: border-box;"><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">EDB-ID:</strong> 39160</td><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">CVE:</strong> N/A</td><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">OSVDB-ID:</strong> N/A</td></tr>
<tr style="background-color: rgb(248, 248, 248) !important; box-sizing: border-box;"><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">EDB Verified:</strong> <span class="fa fa-times" style="-webkit-font-smoothing: antialiased; box-sizing: border-box; display: inline-block; font-family: FontAwesome; font-size: inherit; font-stretch: normal; line-height: 1; text-rendering: auto;"></span></td><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">Author:</strong> <a href="https://www.exploit-db.com/author/?a=8467" style="-webkit-transition-duration: 0.3s; -webkit-transition-property: background-color, box-shadow, border, color, opacity; background-color: transparent; box-sizing: border-box; color: #337ab7; outline: 0px; text-decoration: none; transition-duration: 0.3s; transition-property: background-color, box-shadow, border, color, opacity;">Dennis 'dhn' Herrmann</a></td><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">Published:</strong> 2016-01-04</td></tr>
<tr style="background-color: rgb(248, 248, 248) !important; box-sizing: border-box;"><td style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">Download Exploit:</strong> <a href="https://www.exploit-db.com/download/39160" style="-webkit-transition-duration: 0.3s; -webkit-transition-property: background-color, box-shadow, border, color, opacity; background-color: transparent; box-sizing: border-box; color: #337ab7; outline: 0px; text-decoration: none; transition-duration: 0.3s; transition-property: background-color, box-shadow, border, color, opacity;"><span class="fa fa-file-code-o" style="-webkit-font-smoothing: antialiased; box-sizing: border-box; display: inline-block; font-family: FontAwesome; font-size: inherit; font-stretch: normal; line-height: 1; text-rendering: auto;"></span> Source</a> <span class="fa fa-file-o" style="-webkit-font-smoothing: antialiased; box-sizing: border-box; display: inline-block; font-family: FontAwesome; font-size: inherit; font-stretch: normal; line-height: 1; text-rendering: auto;"></span> </td><td colspan="2" style="box-sizing: border-box; padding: 5px 10px;"><strong style="box-sizing: border-box;">Download Vulnerable App:</strong> N/A</td></tr>
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Linux/x86 execve "/bin/sh" - shellcode 24 byte

Linux/x86 execve "/bin/sh" - shellcode 24 byte EDB-ID: 39160 CVE: N/A OSVDB-ID: N/A EDB Verified: Author: Dennis ...

Roaming Through the OpenSSH Client: CVE-2016-0777 and CVE-2016-0778

Roaming Through the OpenSSH Client: CVE-2016-0777 and CVE-2016-0778

Roaming Through the OpenSSH Client: CVE-2016-0777 and CVE-2016-0778 Papper Link

How to set up NTP server in CentOS

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<span style="color: #0b5394; font-family: Verdana, sans-serif; font-size: large;"><b><u>How to set up NTP server in CentOS</u></b></span></div>
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Network Time Protocol (NTP) is used to synchronize system clocks of different hosts over network. All managed hosts can synchronize their time with a designated time server called an NTP server. An NTP server on the other hand synchronizes its own time with any public NTP server, or any server of your choice. The system clocks of all NTP-managed devices are synchronized to the millisecond precision.</div>
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In a corporate environment, if they do not want to open up their firewall for NTP traffic, it is necessary to set up in-house NTP server, and let employees use the internal server as opposed to public NTP servers. In this tutorial, we will describe how to configure a CentOS system as an NTP server. Before going into the detail, let's go over the concept of NTP first.</div>
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NTP Hierarchy</h2>
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NTP clocks are organized in a layered hierarchy. Each level of the hierarchy is called a <em style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">stratum</em>. The notion of stratum describes how many NTP hops away a machine is from an authoritative time source.</div>
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Stratum 0 is populated with clocks that have virtually no time drifts, such as atomic clocks. These clocks cannot be directly used over the network. Stratum <em style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">N</em> (<em style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">N</em> > 1) servers synchronize their time against Stratum <em style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">N</em>-1 servers. Stratum <em style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">N</em> clocks may be connected with each other over network.</div>
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NTP supports up to 15 stratums in the hierarchy. Stratum 16 is considered unsynchronized and unusable.</div>
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Preparing CentOS Server</h2>
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Now let's proceed to set up an NTP server on CentOS.</div>
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First of all, we need to make sure that the time zone of the server is set up correctly. In CentOS 7, we can use the<tt style="border: 0px; font-family: Monaco, Consolas, 'Andale Mono', 'DejaVu Sans Mono', monospace; font-size: 15px; font-stretch: normal; line-height: normal; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">timedatectl</tt> command to view and change the server time zone (e.g., "Australia/Adelaide")</div>
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# timedatectl list-timezones | grep Australia<br /># timedatectl set-timezone Australia/Adelaide<br /># timedatectl</div>
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Go ahead and set up necessary software using <tt style="border: 0px; font-family: Monaco, Consolas, 'Andale Mono', 'DejaVu Sans Mono', monospace; font-size: 15px; font-stretch: normal; line-height: normal; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">yum</tt>.</div>
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# yum install ntp</div>
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Then we will add the global NTP servers to synchronize time with.</div>
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# vim /etc/ntp.conf</div>
<pre style="background: rgb(238, 238, 238); border: 1px dashed rgb(204, 204, 204); color: #445263; margin-bottom: 15px; overflow: auto; padding: 10px;">server 0.oceania.pool.ntp.org
server 1.oceania.pool.ntp.org
server 2.oceania.pool.ntp.org
server 3.oceania.pool.ntp.org
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By default, NTP server logs are saved in /var/log/messages. If you want to use a custom log file, that can be specified as well.</div>
<pre style="background: rgb(238, 238, 238); border: 1px dashed rgb(204, 204, 204); color: #445263; margin-bottom: 15px; overflow: auto; padding: 10px;">logfile /var/log/ntpd.log
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If you opt for a custom log file, make sure to change its ownership and SELinux context.</div>
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# chown ntp:ntp /var/log/ntpd.log<br /># chcon -t ntpd_log_t /var/log/ntpd.log</div>
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Now initiate NTP service and make sure it's added to startup.</div>
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# systemctl restart ntp<br /># systemctl enable ntp</div>
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Verifying NTP Server Clock</h2>
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We can use the <tt style="border: 0px; font-family: Monaco, Consolas, 'Andale Mono', 'DejaVu Sans Mono', monospace; font-size: 15px; font-stretch: normal; line-height: normal; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">ntpq</tt> command to check how the local server's clock is synchronized via NTP.</div>
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The following table explains the output columns.</div>
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<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">remote</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">The sources defined at ntp.conf. '*' indicates the current and best source; '+' indicates that these sources are available as NTP source. Sources with - are considered unusable.</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">refid</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">The IP address of the clock with which the remote server clock is synchronized with.</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">st</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">Stratum</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">t</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">Type. 'u' is for unicast. Other values may include local, multicast, broadcast.</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">when</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">The time elapsed (in seconds) since the last contact with the server.</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">poll</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">Polling frequency with the server in seconds.</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">reach</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">An octal value that indicates whether there are any errors in communication with the server. The value 377 indicates 100% success.</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">delay</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">The round trip time between our server and the remote server.</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">offset</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">The time difference between our server and the remote server in milliseconds.</td></tr>
<tr style="border: 0px; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; font-weight: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">jitter</td><td style="border: 1px solid black; font-family: inherit; font-size: 15.3000001907349px; font-style: inherit; margin: 0px; outline: 0px; padding: 5px; vertical-align: baseline;">The average time difference in milliseconds between two samples.</td></tr>
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Controlling Access to NTP Server</h2>
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By default, NTP server allows incoming queries from all hosts. If you want to filter incoming NTP synchronization connections, you could add a rule in your firewall to filter the traffic.</div>
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# iptables -A INPUT -s 192.168.1.0/24 -p udp --dport 123 -j ACCEPT<br /># iptables -A INPUT -p udp --dport 123 -j DROP</div>
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The rule will allow NTP traffic (on port UDP/123) from 192.168.1.0/24, and deny traffic from all other networks. You can update the rule to match your requirements.</div>
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Configuring NTP Clients</h2>
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1. Linux</h3>
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NTP client hosts need the <tt style="border: 0px; font-family: Monaco, Consolas, 'Andale Mono', 'DejaVu Sans Mono', monospace; font-size: 15px; font-stretch: normal; line-height: normal; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">ntpdate</tt> package to synchronize time against the server. The package can be easily installed using <tt style="border: 0px; font-family: Monaco, Consolas, 'Andale Mono', 'DejaVu Sans Mono', monospace; font-size: 15px; font-stretch: normal; line-height: normal; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">yum</tt> or <tt style="border: 0px; font-family: Monaco, Consolas, 'Andale Mono', 'DejaVu Sans Mono', monospace; font-size: 15px; font-stretch: normal; line-height: normal; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">apt-get</tt>. After installing the package, run the command with the IP address of the server.</div>
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# ntpdate <server-IP-address></div>
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The command is identical for RHEL and Debian based systems.</div>
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2. Windows</h3>
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If you are using Windows, look for 'Internet Time' under Date and Time settings.</div>
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3. Cisco Devices</h3>
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If you want to synchronize the time of a Cisco device, you can use the following command from the global configuration mode.</div>
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# ntp server <server-IP-address></div>
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NTP enabled devices from other vendors have their own parameters for Internet time. Please check the documentation of the device if you want to synchronize its time with the NTP server.</div>
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Conclusion</h2>
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To sum up, NTP is a protocol that keeps the clocks across all your hosts in sync. We have demonstrated how we can set up an NTP server, and let NTP enabled devices synchronize their time against the server.</div>
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How to set up NTP server in CentOS

How to set up NTP server in CentOS Network Time Protocol (NTP) is used to synchronize system clocks of different hosts over network. All...

Critical iOS Flaw allowed Hackers to Steal Cookies from Devices

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<span style="color: #0b5394; font-family: Verdana, sans-serif; font-size: large;"><b>Critical iOS Flaw allowed Hackers to Steal Cookies from Devices</b></span><br />
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Apple has patched a critical vulnerability in its iOS operating system that allowed criminal hackers to impersonate end users' identities by granting read/write access to website's unencrypted authentication cookies.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhud3SRZemHpKuHpD4FwUnupZozWBMDZmVVcxFPoCfLaqutDaT1ZepZdXqOOVIfiNWgX0MhD_Dl81mEhYGwsO1xuyjN4O-MQBWorhEayB3p4uPnVARNV4q-JdN_G3-Do3DDQjsIyd04jfI/s1600/iOS-Cookie-Theft_www.hackthesec.co.in.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="334" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhud3SRZemHpKuHpD4FwUnupZozWBMDZmVVcxFPoCfLaqutDaT1ZepZdXqOOVIfiNWgX0MhD_Dl81mEhYGwsO1xuyjN4O-MQBWorhEayB3p4uPnVARNV4q-JdN_G3-Do3DDQjsIyd04jfI/s640/iOS-Cookie-Theft_www.hackthesec.co.in.png" width="640" /></a></div>
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The vulnerability was fixed with the release of iOS 9.2.1 on Tuesday, almost three years after it was first discovered and reported to Apple.</div>
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The vulnerability, dubbed "<b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Captive Portal</b>" bug, was initially discovered by <i style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Adi Sharabani</i> and <i style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Yair Amit </i>from online security company Skycure and privately reported to Apple in June 2013.</div>
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Here's How the Vulnerability Worked</h3>
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The vulnerability caused due to the way iOS handles <b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Cookie Stores </b>at <b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Captive Portals</b>, generally a login page that requires users to authenticate themselves before connecting to the free or paid public Wi-Fi hotspots when they are first joining.</div>
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So, when a user with a vulnerable iPhone or iPad connects to a captive-enabled network (<i style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">sample page shown in the screenshot below</i>) – typically at coffee shops, hotels, and airports – a login window is displayed showing terms and conditions over a standard, unencrypted HTTP connection.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjfoMzsRHFZuLEk-j4M3N2oLMoaB2Ro5EDrFngIVUnFZVCsa1wsiEnlJTinxxIKa-7F9xVQmzCEV0L0ujJPasZSttHK0DSEeqzT9ZNLLzkkffUMg7NbE-fPm3odJwVX9Kgksu_CFT5wzNk/s1600/hotel-wifi_www.hackthesec.co.in.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="334" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjfoMzsRHFZuLEk-j4M3N2oLMoaB2Ro5EDrFngIVUnFZVCsa1wsiEnlJTinxxIKa-7F9xVQmzCEV0L0ujJPasZSttHK0DSEeqzT9ZNLLzkkffUMg7NbE-fPm3odJwVX9Kgksu_CFT5wzNk/s640/hotel-wifi_www.hackthesec.co.in.png" width="640" /></a></div>
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Once accepted, the affected user is able to browse the Internet normally, but the embedded browser shares its unencrypted cookie store with the Safari browser.</div>
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According to a <a href="https://www.skycure.com/blog/shared-cookie-stores-bug-fixed-in-ios-9-2-1/" rel="nofollow" style="border: 0px; color: #1177b8; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: none; padding: 0px; text-decoration: none; vertical-align: baseline;" target="_blank">blog post</a> published by Skycure on Wednesday, this shared resource allowed hackers to create their own fake captive portal and associate it with the Wi-Fi network, enabling them to steal virtually any unencrypted cookie stored on the device when an affected iOS device is connected.</div>
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Here's the List of Attacks a Hacker can Perform</h3>
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According to researchers, this captive portal vulnerability allows an attacker to:</div>
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<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Perform an <b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><u style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Impersonation Attack</u></b> – Attackers could steal users' unencrypted (HTTP) cookies associated with a website of their choice, allowing them to impersonate the victim's identity on the particular website.</li>
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Perform a <b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><u style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Session Fixation Attack</u></b> – This means, logging the victim into an attacker-controlled account (because of the shared Cookie Store). When the victims browse to the affected site via the Safari mobile browser, they'll be logged into the hacker's account instead of their own.</li>
<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Perform a <b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><u style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Cache-Poisoning Attack</u></b> on the websites of the attacker's choice (by returning an HTTP response with caching headers). In this way, the attacker could execute malicious JavaScript every time the victim connects to that website in the future via the Safari mobile browser.</li>
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Patch Your Device Right Now!</h3>
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The flaw affected iPhone 4S and iPad 2 devices and later. However, the vulnerability has been resolved with the release of <a href="https://support.apple.com/en-us/HT205732" rel="nofollow" style="border: 0px; color: #1177b8; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: none; padding: 0px; text-decoration: none; vertical-align: baseline;" target="_blank">iOS 9.2.1</a> in which there is an isolated cookie store for captive portals that will keep hackers at bay.</div>
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Skycure says that this is the longest time ever taken by Apple to fix a bug, but the patch was much more complicated than it would be for a typical bug. Though, the company says it has no reports of exploits in the wild.</div>
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So, in order to keep yourself safe from such attacks, <a href="https://support.apple.com/en-us/HT205732" rel="nofollow" style="border: 0px; color: #1177b8; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: none; padding: 0px; text-decoration: none; vertical-align: baseline;" target="_blank">download iOS 9.2.1</a> as an over-the-air update from the Settings menu on your iOS device right now.</div>
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Critical iOS Flaw allowed Hackers to Steal Cookies from Devices

Critical iOS Flaw allowed Hackers to Steal Cookies from Devices Apple has patched a critical vulnerability in its iOS operating system th...

Zero-Day Flaw Found in 'Linux Kernel' leaves Millions Vulnerable

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<span style="color: #0b5394; font-family: Verdana, sans-serif; font-size: large;"><b>Zero-Day Flaw Found in 'Linux Kernel' leaves Millions Vulnerable</b></span><br />
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A new critical zero-day vulnerability has been discovered in the<b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"> Linux kernel </b>that could allow attackers to gain root level privileges by running a malicious Android or Linux application on an affected device.</div>
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<br style="content: ' '; display: block; margin: 20px 0px 0px; outline: 0px; padding: 0px;" />The critical Linux kernel flaw (<a href="http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=2016-0728" rel="nofollow" style="border: 0px; color: #1177b8; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: none; padding: 0px; text-decoration: none; vertical-align: baseline;" target="_blank">CVE-2016-0728</a>) has been identified by a group of researchers at a startup named Perception Point.</div>
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The vulnerability was present in the code since 2012, and affects any operating system with <b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Linux kernel 3.8 and higher</b>, so there are probably tens of millions of computers, both 32-bit and 64-bit, exposed to this flaw.</div>
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However, the most bothersome part is that the problem affects <b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Android versions KitKat and higher</b>, which means about 66 percent of all Android devices are also exposed to the serious Linux kernel flaw.</div>
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Impact of the Zero-Day Vulnerability</h3>
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An attacker would only require local access to exploit the flaw on a Linux server.</div>
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If successfully exploited, the vulnerability can allow attackers to get root access to the operating system, enabling them to delete files, view private information, and install malicious apps.</div>
<blockquote class="tr_bq" style="border-left-color: rgb(232, 232, 232); border-left-style: solid; border-width: 0px 0px 0px 5px; font-stretch: inherit; margin: 0px; outline: 0px; padding: 10px; quotes: none; vertical-align: baseline;">
<i style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">"It's pretty bad because a user with legitimate or lower privileges can gain root access and compromise the whole machine," </i><b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Yevgeny Pats</b>, co-founder and CEO at security vendor Perception Point, said in a <a href="http://perception-point.io/2016/01/14/analysis-and-exploitation-of-a-linux-kernel-vulnerability-cve-2016-0728/" rel="nofollow" style="border: 0px; color: #1177b8; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: none; padding: 0px; text-decoration: none; vertical-align: baseline;" target="_blank">blog post</a> published today.<br style="content: ' '; display: block; margin: 6px 0px 0px; outline: 0px; padding: 0px;" /><i style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">"With no auto update for the kernel, these versions could be vulnerable for a long time. Every Linux server needs to be patched as soon the patch is out."</i></blockquote>
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Usually, flaws in Linux kernel are patched as soon as they are found; therefore, Linux-based operating systems are considered to be more secure than others. However, zero-day vulnerability recently discovered in the Linux kernel made its way for almost 3 years.</div>
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The Cause of the Critical Linux Kernel Vulnerability</h3>
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The vulnerability is actually the result of a <b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Reference Leak</b> in the keyrings facility built into various flavors of Linux. The keyrings facility is primarily a way to encrypt and store login data, encryption keys and certificates, and then make them available to applications.</div>
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However, a reference leak could be abused by attackers to ultimately execute arbitrary code in the Linux kernel.</div>
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So far, the researchers said, no exploits have been discovered in the wild that take advantage of this vulnerability.</div>
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Perception Point has provided a technical analysis of the vulnerability and how one can exploit it, including <a href="https://gist.github.com/PerceptionPointTeam/18b1e86d1c0f8531ff8f" rel="nofollow" style="border: 0px; color: #1177b8; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: none; padding: 0px; text-decoration: none; vertical-align: baseline;" target="_blank">proof-of-concept</a> (PoC) exploit code published on its Github page.</div>
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Patch Expected to Roll Out Soon</h3>
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The good news is that Perception Point has already reported the flaw to the Linux team, and patches are expected to roll out today to devices with automatic updates.</div>
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However, it may take a little longer on Android devices to receive the patch, given the fact that most updates aren’t pushed automatically by manufacturers and carriers.<br style="content: ' '; display: block; margin: 20px 0px 0px; outline: 0px; padding: 0px;" /><br style="content: ' '; display: block; margin: 20px 0px 0px; outline: 0px; padding: 0px;" /><h3 style="border: 0px; font-family: inherit; font-size: 1.4em; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: 35px; margin: 0px; outline: 0px; padding: 0px; text-align: left !important; vertical-align: baseline;">
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Type following commands as per your Linux distro:</div>
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<li style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;"><b style="border: 0px; font-family: inherit; font-size: inherit; font-stretch: inherit; font-style: inherit; font-variant: inherit; line-height: inherit; margin: 0px; outline: 0px; padding: 0px; vertical-align: baseline;">Debian or Ubuntu Linux:</b> sudo apt-get update && sudo apt-get upgrade</li>
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