Friend mine is a super high end security guy... He doesn't talk about it at all, but I suspect NSA.
He was in an airport once and got pinged by someone in the airport. He was able to electronically identify the culprit and from there physically identified him. Broadcast a popup directly to the guys computer describing his clothing and told him you're being watched. Guy packed up and immediately left.
Some day I'm going to spend some time with him securing my network and computers better. He has a dedicated hardwired PC that is ONLY used for financial transactions.