https://en.wikipedia.org/wiki/ECHELON

Established in the 60s so it was kept pretty secret for a long period of time.

It's interesting to think that the government has been using technology to watch us for awhile but now thanks to ubiquitous networks, cheap internet, phone and apps like tinder and strava and a bit of ingenuity, we can watch back. :)

Another instance is one darknet market being taken down by Dutch police. They were also in full control of the next biggest market where they knew everyone would flee to, and they spent some time monitoring all comms on that second site before intervening.