So far, fewer than 1 percent of the work units appear to have been tampered with, but the effort to clean the data have consumed a significant portion of the project's resources.
Now Philippe Golle and Ilya Mironov, both of Stanford University, have developed security schemes to foil cheaters.
In a paper presented last month at a conference in San Francisco, the students said they can verify that distributed computing work, the basis of SETI@home, has been done by inserting special checkpoints, or "ringers," into data packets.
If the processed data is returned to a project like SETI@home without the marker, the organization knows the data was not processed and the results are fraudulent.
The potential for cheating is a research problem for SETI@home and could become a business problem for a growing set of commercial ventures that offer cash or credit to distributed-computer-project participants.
Tedious data cleaning
SETI@home relies on unpaid volunteers, some of whom seek glory on the project's Web page for having processed the most data. As such, it is seductive to hackers and there is little incentive beyond honor for producing quality or reliable results.
Users donate their computers' downtime by downloading and installing software to crunch data collected by a huge radio dish at the
Radio Observatory in Puerto Rico. When operational, the program appears as a vibrant purple signal-graph screensaver on computers. The processed data are returned to the project.The SETI@home folks have caught some cheaters by comparing data processed multiple times to cross-check for matches.
Cheaters' work is thrown out and their SETI@home accounts are canceled. Of course, cheaters could sign up under new usernames.
99.9 percent do not cheat
SETI@home software designers have regularly inserted patches into their software over the years to plug small security breaches, said chief scientist Dan Werthimer.
Other software fixes are intended to detect bad data that might be a result of home computer glitches or Internet problems. These fixes often help to thwart hackers too, Werthimer said.
"Some of the things [Golle and Mironov] propose are things we've already done," Werthimer told SPACE.com, adding that there are also some new security recommendations in the paper that SETI@home may consider implementing.
"It's been a minor nuisance that we've had to deal with these occasional cheaters," Werthimer said, stressing that 99.99 percent of the volunteers do not cheat.
But there's a casual competition via the project's Web site for how many work units a person's computer can process, Werthimer explained. So a handful of people have tried to cheat the system, "even though they haven't actually done that work, so they can kind of get their name in the lights."
Werthimer said the tampering has not compromised any of the project's science. And if the Big Message ever appears to arrive from space via someone's home computer, there's a plan: "If you ever send us a result that says you found ET, we'll just go check the data ourselves," he said.
But improving security is not the only concern. Werthimer said there is only a few months' worth of funding in the SETI@home bank, and further security enhancements would likely take a backseat to continued fund-raising efforts.
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