"Once they learn about retrying it starts to fail," he said. Eggendorfer also compared spam filters to painkillers: "It relieves the symptoms, but doesn't eliminate the cause."
For other types of spam, such as Nigerian 419 scams, this technique may be less effective as these spammers win if they snare a single human sucker, no matter how long it takes. The Spamnet (originally called Spamalot until Monty Python objected) project, from the University of Illinois at Chicago, set out to see if they could consume enough of the spammers' time and resources to make it not worth their while to continue.
The technique was simple enough and easily copied: reply to the spam with email expressing interest and asking for a phone call to a supplied phone number. Doing this manually resulted in as many as 50 email exchanges and numerous phone calls. Similarly, following the links in phishing messages and filling out web forms netted as many as 25 calls from mortgage brokers.
Based on this, the Spamnet group attempted to automate the process by creating three types of agent: Arthur (Nigerian 419), Patsy (web forms), and Lancelot (phishing), and achieved some success in getting spammers to interact with the agents. This technique might allow law enforcement and banks to track down and eliminate the sources of these types of attack.
Both these papers share another helpful characteristic: they do not break email as we know it. Other efforts, such as using multiple filters and detecting the obscured text in image spam (presented by Battista Biggio from the University of Cagliari) also seem promising.
Simpson's next effort, to be released soon, is working on a way to automate a way for senders to tell the receiving server that a message is not actually spam.
"It makes false positives a non-issue," he says.
Still, all the papers made one thing plain: spam isn't going away any time soon, despite all the research being thrown at the problem.
Which is why those outside the profession favour hiring a bunch of programmer-detectives and a couple of trained assassins instead. ®