Web sites are continually reminding us that it's important to choose a strong password. But what makes a password strong? And just how long might it take a powerful computer to crack a strong one, compared with a weak one?

Here's a handy site that can show you. Just type in a password that you might have considered using. As you type, the site shows you just how long it would take to crack on various computers, including a home machine from the 1980s and the current fastest machine in the world.

It's fascinating to see how just a simple change to a password can make it vastly easier or harder to crack. Fred, for example, would take a second to crack, as would Secret. But put them together as Fred-Secret and the time increases to 4 days. Add a 3-digit number to the end, and now the crack time is nearer 30 years.  Read More