iptables core with ssh drop logging

by

/etc/sysconfig/iptables:

*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
:LOGGING - [0:0]

-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT

# here you allow the ssh/22 connections you need
-A INPUT -p tcp -m state --state NEW -m tcp -s IP.YOU.WANT.TOALLOW --dport 22 -j ACCEPT

# remaining 22/ssh connections are sent to logging
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j LOGGING

# recieve and log
-A LOGGING -m limit --limit 6/min --limit-burst 3 -j LOG --log-prefix "[iptables dropped] "

# drop for real
-A LOGGING -j DROP

COMMIT

/etc/rsyslog.d/iptables.conf:

# lets log the dropped connections into it's own file
:msg,contains,"[iptables dropped]" /var/log/iptables.log
 
# stop processing
& stop

/etc/logrotate.d/iptables.conf:

/var/log/iptables.log
{
  rotate 14
  weekly
  missingok
  compress
  delaycompress
  postrotate
        /usr/bin/systemctl kill -s HUP rsyslog.service >/dev/null 2>&1 || true
  endscript
}