Re: Terrorists are not stupid!
Well... Firstly, the Westminster Bridge attacker was just an angry random. Had he been an actual ISIS soldier and probably would have been better outfitted (software and hardware).
Secondly, Yeah i may have underestimated the time taken to write an encryption implementation but they could use one of the many open source implementations that have been security checked by hundreds of people. However creating their own IM that make use of dark networks like Tor (for that additional layer of security) would not be much of a challenge for an intermediate programmer.