While you read these words, the chances are that somebody, somewhere, is trying to break in to your computer by guessing your password. If your computer is connected to the Internet it can be found, quickly, and if it can be found, somebody will try to break in.

And it isn’t like the movies. The criminal hacker trying to guess your password isn’t sat in a darkened room wondering which of your pets’ names to type on their keyboard. The hacker’s at lunch and they’ve left a computer program churning away, relentlessly trying every password it can think of. And computers can think of a lot of passwords.