This is about hiding what they have, how they got it, how they used it, etc. For example, if you discovered the FBI had data that made no sense for them to hav

This is about hiding what they have, how they got it, how they used it, etc. For example, if you discovered the FBI had data that made no sense for them to have, such as an iris scan, you'd not only know they had it, but they they had likely taken it from a distance, and maybe even doing passive scanning too. To be honest, aside from system design vs secret info, not following the position your presenting. To get some idea of how this has to do with sources and methods, look into how Stringray like devices work, how they're used to collect data, how the data is used, etc.