date: 2007-12-30 21:06:19+00:00
'CentOS 5 : preventing brute force attacks with iptables'
categories: - Iptables - Linux - Red Hat/CentOS - Security
The following example is much simpler, it blocks hosts trying to connect more than 3 times to the SSH server within 60 seconds. If you need something more complex, check out the howto mentionned above.
This is my /etc/sysconfig/iptables
<code>*filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] :LIMIT_SSH - [0:0] # accept localhost and related/established traffic -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -i lo -j ACCEPT # transfer connections made to tcp/22 to the LIMIT_SSH chain -A INPUT -p tcp -m tcp --dport 22 -m state --state NEW -j LIMIT_SSH # block anything else in the INPUT chain -A INPUT -j DROP # if host has made more than 3 attempts in 60 seconds, drop it -A LIMIT_SSH -m recent --set --name SSH -A LIMIT_SSH -m recent --update --seconds 60 --hitcount 4 --name SSH -j DROP -A LIMIT_SSH -j ACCEPT COMMIT</code>
Recent module homepage : http://www.snowman.net/projects/ipt_recent/