Callblocking

Callblocking refers to technologies and practices designed to prevent unwanted telephone calls from reaching a user. It can be implemented on mobile devices, landlines, and voice-over-IP systems, as well as by telecommunications carriers. The goal is to reduce interruptions from spam, robocalls, telemarketing, and other unsolicited calls.

Blocking methods include blacklists (numbers that are blocked), whitelists (permitted numbers), time-based rules, and caller-id–based screening. Many devices offer built-in blocking features, such as blocking a contact or restricting calls from unknown numbers, while some systems provide do-not-disturb modes with exceptions.

On smartphones, operating systems provide call-blocking options. Android and iOS allow users to block specific numbers, filter unknown callers, or route blocked calls to voicemail. Carrier-based blocking services can also identify and block suspected spam calls at the network level, often using databases and spam-detection technology, sometimes in cooperation with third-party providers.

Third-party apps and some VOIP services offer additional call-blocking and filtering features, including dynamic spam lists, community reporting, and customizable rules. These tools may classify calls as likely spam and either block them or present a warning to the user.

Limitations include false positives, where legitimate calls are blocked, and evolving spoofing techniques that attempt to bypass simple blocklists. Blocked numbers may be reassigned, requiring ongoing updates. Privacy considerations arise, as blocking data may be collected or shared with providers or apps.

Legal and policy aspects vary by jurisdiction and service provider, covering consent, consumer protection, and telecom regulations. Users should review applicable terms of service and privacy settings related to callblocking in their region.