Personal Identification Number Unlock Keys are unique eight-digit codes linked to each Subscriber Identity Module card. Some device manufacturers refer to PUK codes as PIN Unlock Codes. SIM card owners key in their PUK codes to unlock blocked cards.
Entering an incorrect SIM card PIN three times in a row blocks the card, causing the device to request a PUK code. The SIM card manufacturer prints the PUK code on the SIM card package. However, some mobile networks keep PUK codes secret, and they only reveal them when subscribers call. On the other hand, registered users may obtain their PUK codes from their mobile networks’ websites. A PUK code is required to change the SIM PIN.
A PUK code helps to keep SIM details safe by preventing unauthorized use of subscriber accounts. Keying in an incorrect PUK code 10 consecutive times blocks the SIM card permanently. Although mobile providers normally offer new SIM cards, the process may be lengthy and inconvenient.
Mobile phone subscribers can prevent accidental SIM blocking by deactivating the PIN code request through the phone security settings feature. However, the PIN request should only be deactivated when the user is not at risk of having the phone stolen.