The HOWTO that Andy quoted is very much out-of-date. You would do better to go to http://www.netfilter.org/documentation/ and read the "Linux 2.4 Filtering HOWTO". The site is pretty slow right now, but the document is mirrored elsewhere. It is written by Rusty Russel, the guy who first wrote the 2.4 filtering framework. The tool you need is called iptables. It is most likely packaged separately on your distribution of choice. Another nice tool to have is iproute2, though you don't need it. It exposes some of the more advanced features of Linux advanced routing. ifconfig is sufficient. Viruses... Well, you don't have a whole lot to worry about, but clamav's "clamscan" is the program you want. If you're interested in setting up smtp proxies, look at clamsmtp, which can be set up transparently for SMTP connections or as a proxy through your smtp server. There are a number of plugins you can use with Thunderbird or your favorite imap/pop downloader to feed it through clamscan. In fact, the Firefox extension "Download Statusbar" has an optional virus scanner that you can specify in the preferences. Real-time, live-filesystem scanning is possible, but certainly an advanced topic. Generally, it's not needed. It is sufficient to cron a filesystem scan. In fact, you could probably script up a find script to only scan newer files. Good luck! Chad