The two people who shut down four Washington power stations in December were arrested. This is the interesting part:

Investigators identified Greenwood and Crahan almost immediately after the attacks took place by using cell phone data that allegedly showed both men in the vicinity of all four substations, according to court documents.

Nowadays, it seems like an obvious thing to do—although the search is probably unconstitutional. But way back in 2012, the Canadian CSEC—that’s their NSA—did some top-secret work on this kind of thing. The document is part of the Snowden archive, and I wrote about it:

The second application suggested is to identify a particular person whom you know visited a particular geographical area on a series of dates/times. The example in the presentation is a kidnapper. He is based in a rural area, so he can’t risk making his ransom calls from that area. Instead, he drives to an urban area to make those calls. He either uses a burner phone or a pay phone, so he can’t be identified that way. But if you assume that he has some sort of smart phone in his pocket that identifies itself over the Internet, you might be able to find him in that dataset. That is, he might be the only ID that appears in that geographical location around the same time as the ransom calls and at no other times.

There’s a whole lot of surveillance you can do if you can follow everyone, everywhere, all the time. I don’t even think turning your cell phone off would help in this instance. How many people in the Washington area turned their phones off during exactly the times of the Washington power station attacks? Probably a small enough number to investigate them all.