|Analysts say that the keystroke logging virus could allow hackers to monitor activities of drone operators [EPA]
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."
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."
The US military and intelligence communities have used Predator and Reaper drones, built by privately held General Atomics in San Diego, to carry out increasingly precise attacks on top al-Qaeda officials and other US targets in Pakistan, Afghanistan and Yemen.
Densmore explained: "This is essentially sitting in a trailer, an air-conditioned trailer, on the base where you are isolated from kind of the rest of the base, but you have access to all of the live feeds to the UAV, to the unmanned aerial vehicle, so you're in complete control.
"You stay in that cockpit, so to speak, with support for the entire time that the mission is flying."
Last week, US officials confirmed that Anwar al-Awlaki, an American-born cleric linked to al-Qaeda, was killed in a CIA drone strike in Yemen.
In August, al-Qaeda's second-in-command, Atiyah abd al-Rahman was killed in a drone strike in northwest Pakistan.
Ilyas Kashmiri, an alleged leader of both al-Qaeda and one of its Pakistan-based affiliates, was killed in a suspected US drone strike in June.
The US military has achieved its goal of flying 60 combat air patrols overseas with the unmanned planes, according to one US defence official.