= iptables =

Administration tool for IPv4/IPv6 packet filtering and NAT

== Block IP address ==
{{{#!highlight bash
cat /var/log/auth.log | grep Failed
iptables -A INPUT -s 14.39.42.133 -j DROP
iptables -A INPUT -s 80.94.95.181 -j DROP
iptables -A INPUT -s 77.90.185.59  -j DROP
iptables -L
apt install whois
whois 14.39.42.133 
}}}

=== firewall.sh ===
{{{#!highlight sh
iptables -F
sh mail_failure_ip_list.sh | xargs -i iptables -A INPUT -s {} -j DROP
iptables -L
}}}

=== mail_failure_ip_list.sh ===
{{{#!highlight sh
#!/bin/sh
cat /var/log/mail.log | grep failure | awk '//{print $5}' | sort | uniq | sed 's/unknown//g' | sed 's/://g' | sed 's/\[//g' | sed 's/\]//g'
}}}