> Isn’t Signal FOSS? I don’t know how they’d police that when everyone can just fork it and remove the back door.
If the goal is large scale surveillance, it can be combatted fairly effectively as has been shown with e.g. kino.to and other streaming sites which have gone practivally extinct. The same would happen to websites hosting illegal apps.
If the goal is to go after real criminals this is of course useless. But EncroChat [1] has shown that at least large parts of the criminal world don't seem to have great operation security practices.