We're going to guess your passcode, the set of four numbers you use to get into your iPhone when you unlock it. Ready? Is it 1234? 0000? 1998?
If it's any of those, you may want to change it. A developer named Daniel Amitay runs an app called Big Brother Camera Security that uses its own in-app lockscreen, and he's anonymously been tracking the numbers used there. Thinking that the numbers chosen for that lockscreen are probably similar to the main iPhone lockscreen, he's released some information about what people use, shining some light on what are probably the most common four-digit iPhone lock codes.
It's pretty fascinating -- the easy ones to remember like 1234 and 0000 are the most common choices (just like 123456 and "password" are the most common real passwords), and there's a real trend of using actual years for the password, perhaps the first year you bought the iPhone or created the code. And the numbers were surprisingly similar -- 15% of all passcode sets monitored were represented by just 10 different passcodes, which means that if a hacker punches just 10 codes in and yours happened to be one of those, it's game over for your security.
In other words, if you're really concerned about locking someone out, "1980" isn't going to cut it any more.