Reconnaissance/patrol drones have preset routes like cruise missiles, and upload data by satellite so they don't have to come back in one piece to make the mission a success. There is little comm feed implied and that is easy to secure.

But the real problem is getting rid of all comms: This is an interesting issue. I don't know about those new technology drones, but in a large-scale deployment, they would have to be pretty autonomous: no way a central command would handle 10k+ drones on a battlefield, armies of Nintendo players are eerie. There's just no way a C3I network would support thousands of low-latency video-feeds and order anytime soon. It's just too much bandwidth. What bandwidth is available today is already expensive to get in a secure and stealth fashion: look at the money Thales and Sagem make on C3I chains, it's more than the actual weapons they sell.

A real combat drone would have to handle "high level language" orders like "patrol this area in a random pattern for six hours, freely engaging any moving vehicle on the ground and engaging upon confirmation for others..." A.I. systems still have a long way to go before humans can really delegate such tasks.

Pierre