Set a screen lock on your phone and a PIN for the SIM card
The SIM is the small card in your phone that receives SMS verification codes. If you lose your phone, someone may remove the card, insert it into another phone, receive your codes and reset your accounts one by one. A SIM PIN requires that code when the card is powered on in another phone, blocking this route.
No cost at all. You only need to set the screen lock and t…
After a phone is lost, one of the quickest routes for the finder is to put its SIM into another phone and rece…
No cost at all. You only need to set the screen lock and the SIM PIN once each.
After a phone is lost, one of the quickest routes for the finder is to put its SIM into another phone and receive SMS verification codes. Those codes can let them reset accounts one by one. With a SIM PIN, the card requires the code when powered on in another phone, so the finder cannot use it to receive codes. China's Ministry of Industry and Information Technology reported a real case in October 2020. After a user's phone was stolen, the user did not promptly report the SIM lost, giving criminals time to act. They signed into a government-services app with the phone number and a verification code and obtained the user's identity-card number and other information. They then changed the mobile-service password. After the user later reported the SIM lost, the criminals talked telecom customer service into lifting the suspension. They finally exploited an online-loan platform's password-recovery weakness to reset the payment password and steal loan funds. The ministry used this case to urge users to set SIM passwords promptly and report a lost phone immediately. For the screen lock, the U.S. Federal Communications Commission recommends a strong passcode to restrict access. If the phone is lost or stolen, this can prevent unauthorized use that incurs charges and protect personal data from theft.
工业和信息化部 (2020). 工信部提醒！强化个人信息保护意识. 中国政府网转载工信微报，2020-10-22. https://app.www.gov.cn/govdata/gov/202010/22/464049/article.html；US FCC. Protect Your Smart Device. https://www.fcc.gov/consumers/guides/protect-your-mobile-device
Open source linkSet the PIN under SIM lock in your phone settings. The initial factory code is often 1234 or 0000. After three consecutive incorrect attempts, you need the carrier's PUK code to unlock it. Write the new PIN on paper after setting it. This is grade C because the two sources are official advisories plus a single case, with no study estimating how much money a SIM PIN prevents people from losing. For what to do first after losing a phone, see Item 4 (follow this order after losing your phone).