The cracking or exploring of a telephone system, e.g. trying to get free calls, discover special service numbers or other internal technical information
Crimes committed against telephone company computers with the goal of making free long distance calls, impersonating directory assistance or other operator services, diverting calls to numbers of the perpetrator's choice, or otherwise disrupting telephone service for subscribers
The art of circumnavigating the charging system employed by telecommunication authorities as well as controlling the telecommunications system in general