Bayesian Filters To the Rescue

No matter how your customers use their computers, there is one common denominator that affects them all: spam, which represents as much as 85 percent of all e-mail sent and received, according to the International Telecommunication Union, an agency of the United Nations that extends and improves all forms of telecommunication, among other things.

To help fight spam, an excellent--and free--solution has emerged, inspired by the work of an English minister who died in 1761, the Rev. Thomas Bayes. Bayes, who had received an education in logic and theology, wrote an essay about probability inference, which is a way to calculate the likelihood that an event will occur in the future based on the number of times that event has not occurred in the past. Nearly 250 years later, his theory has become the cheapest and most effective means available to determine whether an e-mail message is spam or a legitimate message.

Other spam filters must be shown a picture of each spam message before they can recognize it, the same way antivirus software works. By contrast, Bayesian spam filters "learn" based on human feedback. The more often you correct a Bayesian filter today, the less often you'll need to correct it in the future.

Let's look at three free software packages that use Bayesian filters to help block spam. I have found these solutions to be more accurate, more reliable and--at least in some cases--less taxing on system resources than similar products.

SpamBayes: Written by Paul Graham, SpamBayes is an e-mail filter designed to work with the Mac OS, Linux/Unix and Microsoft Outlook. While it's possible to get SpamBayes to work with Outlook Express, some technical skill is necessary to install it correctly.

SpamBayes is also the main ingredient in many other products, including commercial e-mail filters. One example is the $28 Inboxer software, which can be used to determine whether a message is spam.

You can find the fully functional and completely free SpamBayes software at spambayes.sourceforge.net.

PopFile: For people who check their e-mail using Outlook Express, Outlook, Netscape, Incredimail, Eudora or any other POP-3-based software, PopFile is a great piece of software that runs in the background and sits "virtually" between your e-mail program and your e-mail server. Modifying PopFile settings requires opening a shortcut that launches your Internet browser. The PopFile interface may seem awkward at first, but its learning curve is quick. Written by John Graham-Cumming, PopFile also offers statistical information through its HTML-based interface. The software, along with instructions on how to install it, can be found in the PopFile store at popfile.sourceforge.net.

Of note, in reaction to people finding PopFile's interface awkward, a man by the name of A. Gandhi wrote an add-on program called Outclass (www.vargonsoft.com/Outclass), which integrates PopFile into Outlook's toolbar so the user no longer has to exit or minimize Outlook to train PopFile.

Mozilla: Many of my customers want to stay away from Microsoft's Outlook and Outlook Express because of e-mail viruses that target those ultra-popular programs. As a result, many have chosen to use Mozilla as a means to check their e-mail. The good news is that since version 1.3, Mozilla has included a built-in Bayesian e-mail filter. As of this writing, Mozilla is currently at Version 1.7 and can be found at www.mozilla.org.

Carey Holzman is president of Discount Computer Repair in Glendale, Ariz.

Spam...And Monty Python?
The term "spam" was taken from Monty Python, the British TV comedy troupe. One sketch featured a couple at a restaurant in which everything on the menu contained Spam, a processed meat product. As the waitress explains all the Spam-enhanced meals, a group of men, dressed as Vikings, begin to sing about Spam—and get louder and louder.

The first encounter of spam as unwanted e-mail occurred in online newsgroups. Large amounts of advertisements—in many cases, the same ads repeated over and over—interrupted the normal flow of conversation. Users inconvenienced by these ads remembered Monty Python's Vikings singing about Spam so loudly that other people in the restaurant could not carry on a conversation. Thus, everyone started referring to these junk messages as spam.