Limiting the number of connections to SSH Server using Iptables
Posted by Mohammad Hafiz mypapit Ismail on 24 Jul 2011 in Computers, GNU/Linux, security, Server, Ubuntu/Debian
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This is the quickest way to limit the number of connection to your SSH server with iptables.
sudo /sbin/iptables -A INPUT -p tcp --syn --dport 22 -m connlimit --connlimit-above 5 -j REJECT
This will only allow up to 5 concurrent connections to the SSH server, subsequent connections will be rejected by iptables, thus this can thwarts Brute-force attempts to your server.
More Articles About Securing SSH Server
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Tags: brute-force, firewall, iptables, linux, secured shell, security, ssh, ubuntu
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July 26th, 2011 at 11:44 pm
You can also use tcpwrapper to control the connection to the service.
July 28th, 2011 at 7:12 pm
Not for Archlinux users: http://www.archlinux.org/news/dropping-tcp_wrappers-support/
November 26th, 2012 at 12:40 am
While running the above command am getting the following error
/sbin/iptables -A INPUT -p tcp –syn –dport 22 -m connlimit –connlimit-above 8 -j REJECT
iptables: Unknown error 18446744073709551615
Am using Amazon AWS EC2 virtual machine, please let me know how i can fix this issue