"Lasers." (although, line of sight, point-to-point communication is admittedly less trivial to interfere with)

The point being that, if "criminal gangs" are up to no good, but they're parting their equipment with off-the-shelf Best Buy and Radio Shack products, they probably aren't programming DSP interfaces, aren't encoding and decoding raw bit streams, aren't masking binary objects with base64 blobs, aren't rolling their own encryption.

Or, if they are rolling their own encryption, they're using Excel spreadsheets to do it. [0]

[0] https://www.theregister.co.uk/2011/03/22/ba_jihadist_trial_s...