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Life Guide U.S. essentials
English

Set a lock-screen passcode on your phone and a PIN on the SIM card

  • Top value
  • Evidence C
  • Saves money
  • Free
  • Takes minutes
  • No willpower

In plain words

The SIM card is the small card inside your phone, and text-message codes arrive through it. If you lose your phone, whoever finds it can pull this card out, put it in another phone to receive the codes, and then reset your accounts one by one. If you set a PIN on the card, then once the card is moved to another phone it asks for this code as soon as the phone starts, and that route is closed.

Cost

Free. Set the passcode and the PIN once each.

What you get

After a phone is lost, the fastest route for whoever finds it is to put the SIM card in another phone and receive your text-message codes. With the codes, they can reset your accounts one by one. If the SIM card has a PIN, a different phone asks for it at startup, and the finder can't use the card to receive codes. The Ministry of Industry and Information Technology (工信部) reported a real case in October 2020. A user's phone was stolen, and the user did not promptly report the SIM card lost. The criminals logged in to a government-services app with "phone number plus verification code" and got the user's ID number and other information. They then changed the phone-service password and tricked customer service into reactivating the card that had been reported lost. Finally they used a flaw in the "reset password" function of an online-loan platform to reset the payment password and took the loan money. The Ministry used this case to remind users to set a SIM card password promptly and to report a lost phone right away. As for the lock-screen half, the advice of the U.S. Federal Communications Commission is to set a strong passcode on your phone and limit who can use it. If the phone is lost or stolen, it keeps others from running up charges and keeps your personal data from being misused.

Notes

Set the PIN in your phone settings under "SIM card lock". The factory default code is usually 1234 or 0000. After 3 wrong tries in a row, you need the PUK code from your carrier to unlock it, so write the code down on paper after you set it. This is rated C because both sources are official reminders plus a single case, and no study has worked out how much loss a PIN prevents. For what to do first when a phone is lost, see §14.4 (the order to follow when your phone is lost).

Evidence grade
C : The author's experience or common practice, without direct literature.
Sources
  1. 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
  2. US FCC. Protect Your Smart Device. https://www.fcc.gov/consumers/guides/protect-your-mobile-device

Translated from the Chinese original. Original book, section 14, tip 3. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer