Malicious caller identification

Malicious caller identification, introduced in 1992 as call trace, is activated by the vertical service code *57 ("star fifty-seven"), and is an upcharge fee subscription service offered by telephone company providers which, when dialed immediately after a malicious call, records metadata for police follow-up. Generally, law enforcement will only act on the trace once a formal police report has been filed in regard to the call.

Source: Wikipedia — Malicious caller identification (CC BY-SA 4.0)