Lock the phone and protect the SIM
A SIM PIN adds a barrier when a SIM is moved to another phone. Check the setup carefully instead of guessing the existing code.
Set a screen-lock code and a SIM PIN, and keep the carrier's recovery information accessible.
The book warns that 3 wrong SIM-PIN attempts require the carrier's PUK recovery code.
Why consider it?
The original book gives practical SIM-lock guidance without an external cited study. The attempt count is an operational warning, not a quantified protection effect; confirm the procedure with your carrier. Incorrect guesses can lock the SIM. No default PIN is recommended and no fraud-reduction percentage is claimed.
Read the sources
Source grade C is reproduced from the original work. It does not establish suitability for everyone.
Original item: chapter 14, item 3 ↗Adaptation: Rewritten in English from the locked Chinese original; retained evidence grade and study limits. Effect sizes quoted from the cited source: no quantified effect of the proposed action is claimed; numbers, where present, are descriptive findings, study procedures or guidance parameters. Original book guidance only; no external evidence or measured prevention effect was cited.
Make space for a practical habit.
Add this idea to your local checklist.