I don’t have a clue what happened, but my little LG phone is now locked and is prompting me to enter a PUK code. What’s a PUK code and where does it come from?
A PUK code is a personal unlocking key and it’s tied to your SIM card. What’s a SIM card? I knew you’d ask that! A SIM card is a subscriber identity module and it’s the tiny little plastic card buried deep in your cellphone, whether a super smart Galaxy S7 or iPhone 7 or a simpler phone like an LG Xpression. Without a SIM card your phone doesn’t exist on the cellular network and with it, your phone’s “identity” is known whether you’re in Kuala Lumpur or Miami Beach.
Problem is, leave your phone alone for two minutes and someone with sufficient knowledge can easily pop the SIM card out and slip it into their own phone, even one that’s quite a different brand, and then masquerade as you on the cellular network. Your phone calls, your text messages, all would automatically route to the new phone because the cellular network itself has no way of confirming that the bad guy’s phone isn’t the real thing. Definitely not good!
Here’s what SIM cards look like, in case you’re not sure:
Back to the PUK: they’re basically the “secret unlock key” for your SIM card and 99% of the time you’ll never even know it exists and is tied to your SIM card because your phone should never prompt you for the PUK. But… sometimes it does.
Worse, the way that the system is designed, you only have ten chances to enter the correct PUK and then the SIM will lock down and be unusable, even in the original phone. Scary! But that’s why when you see a phone prompting for the personal unlock key, it has a countdown timer, as shown here:
Since most folk don’t know what a PUK is, they enter their PIN a few times before they realize something’s wrong, so in fact you’re more likely to see that counter at less than ten, like with this LG Xpression:
It’s getting a bit scary at this point with only 5 attempts left. Get to zero and you’ll need a new SIM card, something the carrier might actually charge you for!
But it turns out that all the major carriers can show you the PUK associated with the SIM of a specific phone directly through the Web site. For an example, I’ll step through the process of finding the PUK for my daughter’s LG Xpression 2 phone through wireless.att.com. Since I have more than one phone on the account, I’ll need to click on the right choice (which is rightmost in their layout):
A click on the Xpression and it shows me an update on the phone’s usage, billing cycle, etc:
As highlighted, you’ll want to click on Manage my device & features to proceed from here.
Apparently AT&T defines “PUK” as “PIN Unlock Key”, which makes sense too. Whatever you want to believe PUK stands for, click on Get your PIN unlock key (PUK) and you’re just about there:
There it is! My daughter’s PUK is 87149024 as shown. AT&T even offers a handy tip on how to enter the PUK so that you can unlock your phone. We tried it with my daughter’s LG Xpression 2 and sure enough, that’s the PUK code!
If you have an iPhone the process is slightly different, as AT&T explains:
Basically they all say “enter it wrong ten times in a row and you’re screwed.” 🙂
So don’t do so. If you see a prompt for a PUK to be entered stop trying to enter different codes and instead jump onto your cellular carrier’s Web site, log in, and retrieve the correct PIN unlock key for that device and SIM card. Done.