"Knowledge that GCHQ exploits these products and the scale
of our capability would raise public awareness generating
unwelcome publicity for us and our political masters."
"our political masters"?! If that is the kind of language bandied around the NSA and GHCQ, you can be sure that people probably don't question the authority of those asking them to do something illegal or at least grossly unethical. It also probably be means that there is a strong culture of "the ends justify the means."
