'Soft' Firewall protection for dedicated servers

[Mr Chunder]

Ok, those of you who run dedicated servers and do not have firewalls on them, what sort of protection would you use. I have some unimportant webservers in this state but I'm wondering whether it would be worth using a software based firewall type product - one that monitors for dubious incoming packets, DoS attempts etc. Anyone recommend anything or have some experience with these ?

[JTY]

If they run Linux, I'd look into iptables, or netfilter..... both of which can be used to lock down a box.