The making of telephone calls, either live or by employing audio tapes with obscene, profane or malicious content, may cause great distress to the receiver. Although it is illegal, with civil or criminal penalties, in many countries, the anonymity of the telephone assists many perpetuators to evade prosecution. The caller may allege to be conducting a survey, or may use a telephone shared with many other users; both these tactics make detection and prosecution more difficult.
Obscene or malicious telephone calls are characterized by considerable inventiveness. They may be expressed in a language foreign to the receiver, or may even be innocuous while attended by auto-erotic acts. The caller may say nothing: a continually ringing phone is in itself stressful. Some degree of compliance by a small percentage of recipients encourages offenders.
In the UK alone about 15 million malicious phone calls are made every year.