block ssh brute force attacs / prevent synflooding 
Tuesday, October 28, 2008, 09:49 - Network, Security
Posted by Administrator
With iptables module recent you can limit the count of tcp connection attempts. In my case i allow only 3 ssh connection attempts per minute. This stops script kiddies doing ssh brute force attacs.
iptables -N synflood
iptables -A synflood -p tcp --dport ssh -m recent --set --name SSH
iptables -A synflood -p tcp --dport ssh -m recent --update \
                     --seconds 60 --hitcount 4 --name SSH -j DROP

iptables -A INPUT -p tcp -m state --state NEW -j synflood
iptables -A FORWARD -i $OUT -p tcp -m state --state NEW -j synflood


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