In 1949 the Hungarian-American mathematician John von Neumann, at the Institute for Advanced Study in Princeton, New Jersey suggested that it was theoretically possible for a computer program to replicate. This theory was later tested in the 1950s at Bell Laboratories when a game called Core Wars was developed. In the game, players created small computer programs that attacked, erased, and tried to reside on an opponent's system. In 1983 American electrical engineer Fred Cohen, at the time a graduate student, coined the term virus to describe a self-replicating computer program. Computer viruses are a sign of vandalism on computer systems