It currently looks like this is a regular virus, which got into the classified network, possibly by use of a flash drive. Given the amount of havoc which the Stuxnet was able to inflict upon Iran's nuclear program, I'm not comfortable that armed drones may be vulnerable to similar hacking by our enemies.
In the past, I brought up the "Battlestar Galactica" scenario (hostile agent inserts malware which disables your combat systems at a critical moment in an attack) and was poo-pooed by people here who said that security measures would prevent that scenario from occurring. The scenario can no longer be considered far-fetched.
As it also prevented the video transmissions to the troops in the field from being intercepted with radio-shack class home video gear...NOT.
So much for Drones replacing human pilots.. It goes to show that we still have the need for pilots.. Imagine we have an air force of drones shut down by virus during a conflict??