major.io words of wisdom from a systems engineer

Adding comments to iptables rules

After I wrote a recent post on best practices for iptables, I noticed that I forgot to mention comments for iptables rules. They can be extremely handy if you have some obscure rules for odd situations.

To make an iptables rule with a comment, simply add on the following arguments to the rule:

-m comment --comment "limit ssh access"

Depending on your distribution, you may need to load the ipt_comment or xt_comment modules into your running kernel first.

A full iptables rule to limit ssh access would look something like this:

iptables -A INPUT -j DROP -p tcp --dport 22 -m comment --comment "limit ssh access"