The US military's unmanned Predator and Reaper drones are continuing to fly remote missions overseas despite a computer virus that has infected their US-based cockpits.

Government officials are still investigating whether the virus is benign, and how it managed to infect the heavily protected computer systems at Creech Air Force Base in Nevada, where US military pilots remotely fly the planes on their missions over Iraq, Afghanistan and elsewhere.

"Something is going on, but it has not had any impact on the missions overseas," said a source, who was not authorized to speak publicly.

Armed tactical unmanned planes have become an increasingly valuable tool used by the US military to track and attack individuals and small groups overseas, but the virus underscores the vulnerability of such systems to attacks on the computer networks used to fly them from great distances.

Rob Densmore, former US navy airman, told Al Jazeera that the infection was a common keystroke logging virus - which registers the keystrokes pilots use to control the unmanned drones from afar.

"It has to have a point of access, so we know that thumb drives - basically USB drives - are used to upload navigational information, guidance information to Predator and Reaper drones.

"And if there's a way somehow that that information, or that thumb drive, can come into contact with a network or with the internet, that's where the danger is because that basically means that information, can be carried across from the Reaper drones."

Caution raised

Analysts say that the keystroke logging virus, in theory, could allow hackers to monitor activities of drone operators.

Wired magazine, which broke the story on Friday, said the problem was first detected nearly two weeks ago by the US military's Host-Based Security System, but there were no confirmed incidents of classified information being lost or sent to an outside source.

Military network security specialists said it remained unclear whether the virus was intentional and how far it had spread, but they were certain it had infected Creech's classified and unclassified machines.

The virus has also resisted multiple efforts to remove it from the base's computer systems.

"We keep wiping it off, and it keeps coming back," a source familiar with the network infection told the magazine.

As a precautionary measure, military drone units at other US Air Force bases have been instructed to stop using them.

"It's getting a lot of attention," Wired's sourc said. "But no one's panicking. Yet."

PHOTO CAPTION

United States drone plane

Al Jazeera