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Overwhelmed and annoyed, e-mail users worldwide are uniting to stamp out the increased flow of spam targeting in-boxes and inundating computer networks with dubious business offers, miracle drug claims, and increasingly naughty and offensive propositions.

"E-mail users are deluged, upset, and angry about spam," said Alex Eckelberry, president of Sunbelt Software, which makes the IHateSpam filtering software.

Mass Messages

But spam fighters appear to have a tough fight ahead of them. According to a recent report by e-mail security firm MessageLabs, spam volume is expected to rival legitimate e-mail this year. In a review of its e-mail threats, MessageLabs said spam currently accounts for 30 percent of all e-mail and will constitute 50 percent of e-mail by July 2003.

What's more, Jupiter Research, a division of Jupiter Media, reports that since 2001 the amount of spam the average e-mail user receives a day has increased from 3.7 to 6.2 messages. That number is due to increase, Jupiter said, and by 2007 e-mail users will receive more than 3900 spam messages yearly.

While these reports are enough to make even hard-bitten e-mail lovers consider switching back to snail mail, other experts say that spam inundation fears are overblown and that highly effective spam-fighting weapons are at hand.

So far there is no consensus, however, on the best methods for fighting spam. Some look to a multitiered approach, such as filtering at the Internet service provider and client levels, with antispam legislation as another safeguard. Others believe one finely honed tool could break the spam business model and restore user in-boxes to their previously uncluttered states.

After all, expecting users to opt in or opt out of mail lists, or actually track down and sue spammers, is too complicated, they say.

The Perfect Filter?

A group of programmers and researchers who gathered at a spam conference at the Massachusetts Institute of Technology in Cambridge last month were looking for the silver bullet, setting their sights on creating a highly effective spam filter.

"Traditionally, people have thought that spam filtering doesn't really work. That changed in the last year," said Paul Graham, organizer of the MIT Spam Conference and an emerging authority on antispam tools. Graham, who lives in Cambridge, wrote "A Plan for Spam" in August of last year.

He and other spam experts are pinning their hopes on Bayesian filters, which scan the entire content of an e-mail, including header and font information, and classify whether a piece of mail is spam.

The goal is to make these filters so effective that the response rate on spam becomes abysmally low, and spamming becomes a financially prohibitive venture.

"Make no mistake about it--spam is a business," research scientist William Yerazunis told attendees at the MIT conference.

Yerazunis, who works at the Mitsubishi Electric Research Laboratories in Cambridge, hopes to bankrupt that business by proliferating a Bayesian filter based on a programming language he wrote called CRM114. He claims the filter he created using CRM114 can block 99.9 percent of spam, with a similar rate for avoiding false positives.

Getting Personal

False positives, or wanted e-mail incorrectly identified as spam, is the key metric when it comes to evaluating antispam tools because the personal cost of missing correspondence from friends, family, or business associates is high.

And as spam conference speaker Jason Rennie pointed out, dealing with spam is not simple, in good part because the definition of spam is personal.

Rennie, an MIT graduate student in computer science working on spam filters, underscored the importance of being able to personalize spam filters to some degree, by allowing end users to dictate what they consider to be spam. A lot of filter makers, and ISPs that offer spam-fighting tools, are taking pains to ensure their clients have as much say as possible about what winds up in their in-boxes.

Although stopping the onslaught of spam is crucial to ISPs' business, given the bandwidth costs of delivering all that unwanted mail over their networks, it is also essential to ISPs not to inadvertently block legitimate e-mail through overly aggressive filtering.

Jim Anderson, vice president of product development for EarthLink, said the spam problem is a major issue at his company.

According to Anderson, EarthLink blocked and deleted 250 million pieces of spam last November alone, and the company is still hearing from customers that they want more controls.

"But the public policy aspect of the spam challenge is that you don't have unintended consequences," he said.

High on the list of unintended consequences for ISPs is losing customers who feel that not all their legitimate mail is getting through.

Built-In Filters

For Atlanta-based EarthLink, the solution was offering customers a filter, dubbed Spaminator, that blocks 70 percent to 80 percent of spam from user in-boxes and sends them to a "gray folder" that users can peruse to make sure none of their wanted mail has been trapped.

Other e-mail service providers offer the same kind of service. Yahoo, for example, employs its proprietary SpamGuard filter, which sends spam to a "bulk mail" folder in user in-boxes so customers can still dictate what they think is spam.

In addition to offering SpamGuard to its free e-mail customers, Yahoo offers premium mail customers even more stringent filtering tools. Additionally, the company recently added a "this is spam" link within e-mail messages, allowing them to report an offending missive to Yahoo for future blocking purposes.

"Yahoo has taken a holistic approach to combating spam," said Lisa Pollock, director of Yahoo's Messaging Products.

The multifaceted approach seems to be working. Yahoo caught five times more spam in November 2002 than it did in January of that year, according to Pollock.