Wired's Danger Room points out that US Predator and Reaper drones have been under attack by a computer virus:
To date, the virus has only apparently been logging the keystrokes of the operators. From the article, I get the impression that it is the operators workstations and not the drones themselves that are the subject of the attack. Wasn't this how computers took over the world in Terminator 3? Or was that Terminator 4? I can never remember.