The technique of monitoring telephone and radio traffic is known as interception and includes the physical wiretapping of landlines and the scanning of wavelengths to eavesdrop on a target. Since the end of the Cold War and the expansion of other means of electronic communications such as fax, text messaging, and email, interception has become more sophisticated to overcome routine encryption and frequency-hopping technology intended to provide protection.
Legislation authorizing interception invariably places a burden on telephone companies and internet service providers to retain comprehensive electronic records for subsequent scrutiny by law enforcement agencies. However, many countries conduct interception operations overseas in violation of local sovereignty, but outside the legal jurisdiction of their own courts.