How easy would it be for a thief to guess your four-digit PIN? If he were forced to guess randomly, his odds of getting the correct number would be one in 10,000—or, if he has three tries, one in 3,333. But if you were careless enough to choose your birth date, a year in the 1900s, or an obvious numerical sequence, his chances go up. Way up.

Read the whole story at Slate