SAN FRANCISCO -- NASA confirmed on Wednesday that a computer virus sneaked aboard the International Space Station only to be tossed into quarantine on July 25 by security software.

A "worm type" virus was found on laptop computers that astronauts use to send and receive email from the station by relaying messages through a mission control center in Texas, according to NASA spokesman Kelly Humphries.

The virus is reported to be malicious software that logs keystrokes in order to steal passwords or other sensitive data by sending the information to hackers via the Internet.

The laptop computers are not linked to any of the space station's control systems or the Internet.

"The bottom line is it is a nuisance for us," Humphries told AFP. "The crew is working with teams on the ground to eradicate the virus and look for actions to prevent that from happening in the future."

The virus had no adverse effect on space station operations, according to Humphries.

The space station orbits Earth once every 90 minutes at an altitude of about 350 kilometers (217 miles).

NASA is reportedly looking into whether the virus got into the computers by hiding in a memory drive used to store music, video or other digital files.

Humphries said this is not the first computer virus stowaway on the Space Station.

"This is not a frequent occurrence but it has happened before," Humphries said.