Free porn solution. (Technology).

NO, THIS IS NOT AN OFFER for a complimentary aphrodisiac drink. But now that I have your attention, I'd like to recommend a cheap and easy way to block unwanted and dangerous Internet content.

By now, almost everyone realizes that when you give your users access to porn sites, software downloads, and other Internet temptations, it can cost you more than lost productivity; I don't know of any solution that offers perfect protection, but there are many free software packages that will get you within spitting distance.

Here's the combination I typically recommend. Start with Linux, add IP Tables (www.iptables.org) firewall rules with the help of the IP Tables configuration tool gShield (http://muse.linuxmafia.org/gshie1d.html). Then mix in a Web proxy and cache called squid (www.squid-cache.org) with the filtering proxy DansGuardian. You can block viruses, Trojan horses and other potentially dangerous e-mails with Anomy (maiitools.anomy.net). Add SpainAssassin to kill off that last bit of unwanted content.

You can configure these Linux-based Internet gateways as your firewalls or just put them behind your current firewalls. The squid proxy server adds a level of protection by letting users browse the Web without giving them direct access to the Internet, but that's not why I recommend it. We're after its performance-enhancing Web cache.

The Squid cache is especially useful if you have multiple pipes to the Internet, such as a T1, a T3 and a satellite, because multiple Squid caching servers can cooperate with one another. You can set up your Squid caches so that if your T1 line goes down, the proxy for that line will automatically redirect requests to one of the other proxies, such as the one connected to the T3. It may seem redundant to daisy chain DansGuardian into this mix, since DansGuardian is also a proxy. But DansGuardian adds intelligent content filtering that the Squid cache lacks, and you get this feature at very little performance cost in added latency.

The pearl in DansGuardian is that it examines everything that passes through the proxy, not just URLs. You can define custom search expressions that check for combinations of words within a Web page, and ...