The unmanned Predator, which killed the American attack planner, and the Reaper crafts are still able to complete missions over Yemen, Afghanistan and other warzones.
But each keystroke made by pilots, who operate the drones remotely from a base in Nevada, is said to be recorded by the virus and experts are struggling to remove it.
Specialists think the infection has hit both classified and unclassified machines at the base.
This means that some of the data captured by the virus may have been transmitted to the internet and could be available to terrorists online. Read More