SIM Lock / Number Lock
A carrier security feature that prevents your phone number from being ported to another carrier or SIM card without additional in-person verification, protecting against SIM-swap fraud.
Also known as: port freeze, SIM swap protection, number lock
Last reviewed: 10 June 2026
After the rise of SIM-swap fraud, several mobile carriers introduced optional or automatic account-level locks that block number porting requests unless additional verification — often an in-person visit to a store with photo ID, or a pre-set PIN — is provided. The feature is marketed under various names: SIM lock, number lock, port freeze, or SIM swap protection.
Enabling this feature directly addresses the attack surface exploited by SIM swapping: an attacker who phones the carrier's support line with your personal details will be told the account is locked and the number cannot be ported remotely. This adds a meaningful physical barrier for most attack scenarios, since attackers typically rely on remote channels.
Consumers should contact their carrier to enquire about available porting-protection features and activate them proactively. In parallel, reducing reliance on the phone number as an MFA method for high-value accounts provides defence in depth, so that even a successful SIM swap does not immediately expose those accounts.
Sources
- FCC — Cell Phone Fraud (SIM Swap & Port-Out) — Federal Communications Commission
- FTC — Phone Scams — Federal Trade Commission
- Scamwatch — Account or Identity Takeover Scams — Australian Competition & Consumer Commission (ACCC)
- CISA — Recognize and Report Phishing — Cybersecurity and Infrastructure Security Agency