An executive at Microsoft has an unusual idea for beating spammers. Powerful software tools and supercomputers aren't involved, but kittens are.

Or rather, photos of kittens. Kevin Larson, a researcher at Microsoft's advanced reading technologies group, has found that asking a user to identify the subject of a photo, like a kitten, could help block spam programs.

Currently, services like Microsoft's free e-mail service Hotmail require new users to type in a string of distorted letters as proof that it's a human signing up for the account and not a computer. Called Human Interactive Proofs (HIP), Microsoft, Ticketmaster and a host of other companies have been using the system for around five years, Larson said. He spoke in Seattle on Friday at TypeCon 2007, an annual conference put on by the Society of Typographic Aficionados for type enthusiasts and designers.

When Hotmail first started using HIPs, the number of e-mail accounts generated on the first day dropped by 20 percent without an increase in support queries, Larson said. That was a sign that the HIPs were fooling the computer programs that spammers use to automate signing up for new Hotmail accounts from which spam is sent. However, spammers learned how to tweak their programs to better recognize the HIPs, he said.

Now, it's a race for Microsoft to continue to alter its HIP system to fool the computers, which ultimately seem to catch on. Larson's group at Microsoft experiments with different ways to distort the text used in HIPs in a way that is easy for humans to read but difficult for computers.

One twist on the HIP idea that they've worked on is to display 16 or more photos and ask for identification of the photos. In an example, he suggested using pictures of cats and dogs. The problem with the concept, however, is that Microsoft would have to create a massive catalog of photos, otherwise the programmers could match the correct response with each photo in the catalog and begin to spoof the system, he said.

Audience members had a variety of ideas for ways to expand on the idea in order to try to beat the spam programs. One suggested that Microsoft continually take videos of a kitten jumping around a room, as a way to generate a nearly endless string of photos for identification.

The IDG News Service is a Network World affiliate.