Companies and consumers alike have been looking to two primary aids in the battle to stem the flood of spam. On the practical side, they're turning to a seemingly endless parade of filters and other software products designed to slow the tide of unwanted E-mail by doing things such as checking messages against known spam, using textual clues to glean whether a message is spam, or blocking the IP addresses of known spammers. On the more hopeful side, they're pressuring legislators for federal laws banning spam.

IBM researchers say both approaches miss the target--that the software approach amounts to a constant game of trying to stay one step ahead of spammers, while legislation, if and when it comes, won't be able to address spam coming from outside U.S. borders. As a result, they've come up with another approach: Make spammers pay to send messages. It sounds absurdly simple, and Scott Fahlman, a research staff member at IBM's Watson Research Center, says it is. Fahlman is trying to build momentum behind a concept he's calling the "charity stamp" approach, which would force anyone sending unsolicited messages to pay to reach recipients participating in the program unless they had an authenticated code.

Fahlman has written a basic algorithm that could be used in software that would sit somewhere between the recipient's desktop and the supporting mail server or Internet service provider. It would sniff incoming E-mail and determine first whether a message is part of a recipient-defined whitelist of approved addresses. Those messages not on the list then would be scoured for a 10-digit code obtained from one of two sources--the above-mentioned software, or a "charity stamp" site that would issue authenticated codes for a fee. That fee, says Fahlman, would need to be small enough to be acceptable to legitimate E-mailers but large enough to prove too painful for spammers. Those messages lacking any authentication would be returned to the sender with a link to the charity stamp site and a statement that a stamp was needed for the message to be accepted.

Fahlman's vision is for the site to be managed by a nonprofit entity--hence the term charity stamp--thus turning the battle against spam into a potentially powerful fund-raising tool. Once built, the site would let E-mailers set up prepaid accounts and then use those funds to obtain stamps each time they wanted to get an E-mail through to an unknown recipient. Fahlman is trying to gain support within IBM for development of both the software and the Web site needed to get the system off the ground, but he's prepared to go outside IBM in search of companies that will take on the project. "The whole spam industry depends on spam being free to the sender," Fahlman says. "If we change the social rules of E-mail just a tiny bit, I think the whole problem of spam goes away."