At least on paper they can't investigate against any random people. Germany is still considered a nation of law. They need to report to that panel on secret se

At least on paper they can't investigate against any random people. Germany is still considered a nation of law. They need to report to that panel on secret service affairs in parliament I've mentioned, and there are laws in place for what they are allowed to look for (even you could construct something arbitrary at any time against anybody as we saw in the past; if someone needs a reason for an investigation they will find one for sure). On the other hands side, as I said, as nobody can really control what they're doing hell knows what kind of data they collect. If someone (like a board of inquiry after some scandal) asks to much questions and wants to look into things they would shred the records likely again, and every involved person "couldn't remember" anything (that last thing is a common trope before parliamentarian boards of inquiry anyway).