Hitting something quickly with a flat object; or in modern usage, falsely reporting an emergency to send police to someone's address as a prank or attack.
From 'swat' (to hit), which may be imitative in origin, the term has been used since the early 1900s; the cybercrime meaning emerged in the 2000s.
Swatting as a crime is terrifying because it weaponizes emergency services themselves—pranksters make fake 911 calls claiming hostages or bombs, turning the police response into an attack tool, and it's killed innocent people mistaken for criminals.
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