Spycheck

A method of behaviour in the multiplayer game Team Fortress 2. Spycheckers will randomly attack all friendly players in the hopes of finding a spy. They spend a good deal of effort for a few amount of points, and such behaviour is probably motivated by past traumatising experience of being backstabbed by enemy spies.

In the popular multiplayer shooter Team fortress 2 made by VALVe, you can choose a class named spy, and that spy can turn himself invisible. So it is impossible to spot him and so there is a pyro class which can set invisible spy on fire and make him visible for other clases