US air force drones
Airmen use a ground control station cockpit to control remotely piloted aircraft during a training mission at Creech Air Force Base Isaac Brekken/Getty Images

Update: This report was mistakenly based on a 2011 article from Wired and presented as contemporary news.

The US military drone fleet has reportedly been infected with a computer virus which keeps returning despite efforts to remove it.

Wired.com reported in 2011 that the military's Host Based Security System had detected the virus in September in both classified and unclassified systems at Creech Air Force Base, in Nevada.

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The virus which has infected the cockpits of the Predator and Reaper drones, logs pilots' every keystroke as they remotely fly missions.

First detected nearly two weeks ago by the military's Host-Based Security System, the virus has not prevented pilots at Creech Air Force Base in Nevada from flying their missions overseas.

So far the issue has not appeared to affect overseas missions by interfering with pilot navigation and no classified information has been leaked.

Specialists are looking at whether it was due to malware or a 'keylogger' that entered into the code either on purpose or by accident.

If it is due to a keylogger, classified data may have been logged and risks being leaked to an outside agent.

A source told Wired: "We keep wiping it off, and it keeps coming back. We think it's benign. But we just don't know."

Spokesman for Air Combat Command, Lt. Col. Tadd Sholtide said: "We invest a lot in protecting and monitoring our systems to counter threats and ensure security, which includes a comprehensive response to viruses, worms, and other malware we discover."

Drones are a key part of US military policy allowing enemies to be targeted without putting American lives at risk. Since 2008, drones have killed more than 2,000 suspected militants and civilians, the Washington Post reported.