I should say that iptables saved my neck again when I was next to be on the mattress...

At work I manage a network of 400 workstations with windows, last friday I got a windows worm (spreading fast) which started to spam and after a few hours I got banned in the black list of spamcop having a DOS of mail inside my network. In the meantime of cleaning out each box I used iptable's recent module to avoid getting into black list again... a tutorial of recent usage is here  ¶ 1:08 AM