[icebraining]

Right now taking control is not that hard[1], since most quadcopters are unprotected, but I suspect more autonomous versions (which are supposed to fly without line-of-sight by the operator) will probably only accept encrypted and authenticated packets.

[1] http://samy.pl/skyjack/

[dirktheman]

Parrot AR Drones work by creating a dedicated WiFi access point. It's not that hard to hack into. Because of the limited range of the WiFi signal, I'd still classify AR Drones as toys.

The vast majority of RC planes, cars, multirotors, etc. work with a 2.4Ghz transmitter (TX) and receiver (RX). In the old days you'd claim a frequency, put the corresponding crystal in your TX, and hope that nobody else would use that frequency. Nowadays we have Direct Sequence Spread Spectrum (DSSS) or Frequency Hopping Spread Spectrum (FHSS) to ensure that you're not interfering with someone else's TX/RC. These signals are a lot more difficult to hijack.

GPS Spoofing is probably a better way to hack into UAV's. The Iranians caotured a Sentinel UAV in 2011 with this method: http://en.wikipedia.org/wiki/Iran%E2%80%93U.S._RQ-170_incide...