First of all, the on-board computer systems are encrypted. Second of all, even if you knew how to defeat the encryption, you would also need to have the proprietary software to fly the thing, which includes proprietary hardware the software is sitting on. Meaning, there is no way to interface with the device.
In case you missed the story, in October Wired.com ran an article saying some US drones had been infected with malware - the type malware that steals passwords and other information.
From at least October we know that some US drones have been compromised, how severely compromised, I do not know.
Who designed the guidance systems for the drone? Was it outsourced to china or india? How secure is the company that designed the drone systems?
Before you can BS on something, you need to know the facts.
As far as we know, some mole from the chinese government went to work for the contractor that designed the guidance systems for the drone. The malware infection that was reported back in october allowed someone to take control of the drone and land it safely so it can be delivered to china.
With all of the outsourcing the US does, how do we know our systems are secure? We do not even build our own hardrives and motherboards.