Menu

PREVENT BRUTE-FORCE SSH ATTACKS

Prevent (or at least slow down) a brute-force SSH attack.

By default, iptables on a CentOS 6 SSH server allows all inbound SSH traffic on port 22. See /etc/sysconfig/iptables:
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
Modify /etc/sysconfig/iptables to the following in order to allow a particular IP to initiate 5 new SSH connections within a window of 60s. If additional new SSH connections are opened for that IP, then all packets from that IP will be dropped, and the incident will be logged to /var/log/messages. After 60s that IP will be able to open 5 new SSH connections, and so on. 
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -p tcp --dport 22 -m state --state NEW -m recent --set --name SSH -j ACCEPT
-A INPUT -p tcp --dport 22 -m recent --update --seconds 60 --hitcount 5 --rttl --name SSH -j LOG --log-prefix "BRUTE_FORCE_SSH"
-A INPUT -p tcp --dport 22 -m recent --update --seconds 60 --hitcount 5 --rttl --name SSH -j DROP
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT
# service iptables stop && service iptables start
www.hackthesec.co.in

About Author:


I am a Linux Administrator and Security Expert with this site i can help lot's of people about linux knowladge and as per security expert i also intersted about hacking related news.TwitterFacebook

Next
Newer Post
Previous
Older Post

0 comments:

Post a comment

 
Top