Everyone (and their mother) has discovered AIS signals. When there is a major confrontation at sea, or a ship gets stuck in the Suez Canal, it's a race to the data used to track ships. But like any form of Open Source Intelligence (OSINT) the signals you get may be misleading. They may even be fake.

In fact tat is happening more and more frequently. Here's how.

Article on Yantar spy ship http://www.hisutton.com/Yantar.html