Oh yes, I forgot to mention that Jon Griffin also wrote about this at http://www.jongriffin.com/static/linuxnotes. (Maybe you can pester him to update his notes for kernel 2.4 if he's using it.) There's other stuff that you should do (like enabling SYN cookies, turning off ping and broadcast requests, etc.), but I'll leave it to you to read the material that's already out there.
