Tattle-tails were common during the cold war from Vietnam to the fall of the Berlin Wall. They were Soviet intelligence gathering ships; ugly trawler types of a few hundred tons. They followed our carrier battle groups in general and the carrier itself in particular. They bristled with antennas to monitor communications and record every move we made and provide targeting information. They often followed close in the wake of the carrier. Our aircraft often had to literally fly over them in order to trap aboard. They knew before next of kin knew, if a US aircraft had a mishap.
The carrier could always outrun the tattle-tail if need be, but eventually they always caught up. We really, really looked forward to the order to wax the commie bastards.