A virus designed to swipe passwords from online gamers has inexplicably popped up in some laptop computers aboard the International Space Station.

The low-risk virus was detected on July 25, but did not infect the space station's command and control computers and poses no threat to the orbiting laboratory, NASA officials said.

"This is basically a nuisance," NASA spokesperson Kelly Humphries told SPACE.com from the agency's Johnson Space Center in Houston.

According to a NASA planning document obtained by SPACE.com, the worm was identified as W32.Gammima.AG. The California-based retail anti-virus software manufacturer Symantec describes it as a Windows-based worm which spreads by copying itself onto removable media. It is capable of stealing passwords for online games and is classified as a very low risk, according to Symantec's Web site.

Humphries said that while NASA security protocols prohibit discussing details of the virus and efforts to combat it, a search is under way to find out how it got on board the space station more than 200 miles above Earth.

"We'll do our best to track down how it got there and close that gateway," Humphries said. "This is not a frequent occurrence but we have had viruses that have made their way on board before."

New flash memory cards due to launch to the station aboard a Russian cargo ship next month have been screened for the virus, the NASA document stated. Not all of the 71 laptop computers currently aboard the station run Windows, and those that do and are vulnerable to viruses could be updated, it went on.

The space station is currently home to three astronauts: Russian cosmonaut commander Sergei Volkov, cosmonaut flight engineer Oleg Kononenko and NASA flight engineer Greg Chamitoff. Volkov and Kononenko are due to return to Earth in October, while Chamitoff is slated to stay until his replacement arrives during NASA's planned November space shuttle mission.

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