Fail2ban

Fail2Ban Installation from GitHub (EN)

In case an existing Fail2Ban server is running:

sudo service fail2ban stop

Download version 0.10 from GitHub:

wget https://github.com/fail2ban/fail2ban/archive/0.10.0.tar.gz -O fail2ban-0.10.0.tar.gz

Unpack and install:
<source>sudo tar -zxpvf fail2ban-0.10.0.tar.gz

cd fail2ban-0.10.0

sudo python setup.py install

This will install Fail2Ban into the python library directory. The executable scripts are placed into /usr/local/bin and configuration under /etc/fail2ban.

Enable fail2ban as an automatic service:

sudo cp files/debian-initd /etc/init.d/fail2ban

sudo update-rc.d fail2ban defaults

sudo service fail2ban start

Using IP sets instead of Iptables chains

By default Fail2Ban uses Iptables chains to block IP addresses.

Example:

root@fwserv1:~# iptables -S
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-N f2b-sshd
-A INPUT -p tcp -m multiport --dports 22 -j f2b-sshd
-A INPUT -m set --match-set fail2ban-ssh src -j DROP
-A FORWARD -m set --match-set fail2ban-ssh src -j DROP
-A f2b-sshd -s 120.52.56.124/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 116.193.161.242/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 14.215.237.205/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 118.244.238.18/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 155.133.82.12/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 49.4.6.132/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 118.244.206.22/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 61.132.29.162/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 192.160.102.169/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 162.247.72.213/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 149.56.223.241/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 27.255.79.82/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 211.104.171.220/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 187.252.208.82/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -s 116.6.49.126/32 -j REJECT --reject-with icmp-port-unreachable
-A f2b-sshd -j RETURN
root@fwserv1:~#_

Since Linux Kernel 2.6 there is an option to use so-called IP sets to hold big amount of IP addresses in the memory.