Pretty ironic that they got caught after going out of their way to buy secure phones and use secure messaging services when an off-the-shelf iPhone and Whatsapp/Signal/Telegram would have made them 100% untraceable.
One of the features the phones had was that they could be remotely deleted and were locked down to prevent other apps on them. So an off the shelf iphone with signal is going to be vulnerable to having the device itself hacked via text message, bluetooth, or something else in a way the Sky ECC phones theoretically can't be, so it's not necessarily a slam dunk.
A cheap netbook from a no-name Chinese OEM, running weird software you've never heard of named 'TAILS' which doesn't auto-update or anything, and which the makers say is very secure.
A cheap phone from a no-name Chinese OEM, running weird software you've never heard of named 'Sky ECC' which doesn't auto-update or anything, and which the makers say is very secure.
You've got to be fairly knowledgeable to appraise the two options correctly.
Probably Signal would have been a safe bet. Telegram doesn't do encryption by default (on group messages? Been a year or two since I've used it). And Facebook complies with law enforcement agencies, and I don't think it's unreasonable for them to have a feature flags to selectively and transparently disable encryption for some participants if need be.
Facebook certainly likes to at least have sense to know what you are conversating about. Sometime in 2016 we and my buddy abroad got our accounts frozen "due to security reasons" at exact same time; what we were doing is having fun with FB Messenger and sending each other PGP-encrypted messages. This least about 2 months and my buddy is Egyptian, so I am pretty sure at some point FB said "we don't know what they chat about and enough is enough". I got my account recovered after multiple layers of verification including video-call to hold up my ID done by third-party ... my friend never gotten his reinstated.
Facebook definitely has some kind of chat monitoring and real-time censorship in place. For example, I once couldn't send a message in private chat if it included a link to one of the online weed stores. Remove the link, and it goes through just fine. Put the link there, and the thing just hangs and errors out with no coherent explanation.
I suppose the hope is that if relatively good people, maybe bad actors but with certain limits, if they get exposed to or inadvertently the "opportunity" to be involved in higher orders of magnitude of bad - that they may then act as a light that helps create cracks in the armour to expose such horrific behaviour?
