[bell-cot]

Maybe sometimes? With how many bugs are normally found in very complex code, would a rational spy agency spend the money to add a few more? Doing so is its own type of black op, with plenty of ways to go wrong.

OTOH, how rational are spy agencies about such things?

[max_]

Yes. Of course not all.

But some just happen to work too well.

But governments do have blatant back doors in chips & software.