How it works
SIM swapping redirects a mobile number to a SIM or account controlled by someone else through an unauthorized carrier change. It differs from physically stealing the phone. An attacker who receives the number’s calls or texts may try to use them for account recovery or SMS-based verification.
A practical example
A phone may unexpectedly lose normal service while its owner receives notice that the number was activated elsewhere. This could also have an ordinary technical cause, so it needs confirmation. If it is an unauthorized change, accounts relying on that number may require attention as well as restoring the mobile service.
What to check
Contact the carrier through independently verified support using another connection if necessary. Ask whether a SIM replacement or number transfer occurred and secure the carrier account. Review important email and financial accounts through their genuine services. Use available carrier account protection and stronger supported authentication methods that do not rely solely on that mobile number.
Limits and safe use
Poor signal alone does not prove SIM swapping. A device PIN protects the handset but is not necessarily the same as a carrier account security PIN. Restoring phone service does not automatically terminate every account session created during the incident. Document the timing and coordinate account recovery separately with the relevant providers.