wallhack

A form of game cheat especially associated with first-person shooters like
Quake, in which the walls in the simulated maze or dungeon are rendered
transparent to the cheater. This gives the cheater normally hidden
information about the whereabouts of other players. Beyond gaming, a  is the
paradigm case of a whole class of security problems that stem from the fact
that a server cannot trust client software, and server authors must assume
that all computation farmed out to a client is exposed to and can be
interfered with by the user.

