Autodialer / War Dialing

War dialing originated in hacker culture as the practice of having a computer dial every number in a telephone exchange to find modems or fax machines. Modern autodialing software performs the same function at internet scale: millions of numbers can be called per hour to identify live lines, voicemail systems, and vulnerable PBX hardware. Scammers use the results to build verified lists of active numbers for robocall campaigns, and criminal groups sell these lists commercially.

Autodialing also enables harassment and intimidation campaigns, and the technique is central to most large-scale telephone fraud operations. Under US law, the Telephone Consumer Protection Act (TCPA) restricts autodialers from calling mobile numbers without prior consent, but offshore operators largely ignore domestic regulation. Carriers and the FCC have introduced analytics-based call-blocking that identifies autodialing signatures and labels or blocks the calls.

For individuals, the best defence is not answering calls from unknown numbers and allowing voicemail to filter them. If a number appears in the National Do Not Call Registry and still receives autodialed calls, a complaint to the FTC is appropriate. Call-blocking apps that use community-sourced spam databases can dramatically reduce unwanted contact.