Like it or not, massive leaks of passwords are everyday bread for some services. It wouldn't present such a threat to their users - websites such as Last.fm often advise you to change your password - had it not been for the fact that we love to use the same password with a couple of accounts.
Unfortunately, we would rather take the risk of losing sensitive data than memorize a bunch of passwords. Nowadays, crackers often don't have to use pass generators and attack the websites using brute force methods. All they have to do is to find your e-mail adress and one of your passwords - they might have already found their way onto one of those shady lists on the dark side of the Internet.
How to make sure you won't fall victim? The solution to this problem is actually quite obvious: one account = one pasword. Your password ought to be strong - there should be letters (also capitalized) and numbers - and long. One of the deadly sins when it comes to picking a password is choosing a typical word that appears in a dictionary, as well as a name. No more "susan1989" or "sweetkitty"!
Afraid that memorizing a dozen of complicated passwords is not possible? Get used to password managers such as LastPass or KeePass.
If you want to check whether your password and login can be found somewhere in the Web, use PwnedList. Type in your e-mail address, and the program will check for you whether there is some data concerning your password in the Internet. You don't trust some websites and don't want to provide them with your e-mail address? Code your login with SHA512 generator first.
If your password and e-mail cannot be found in the data base, you will be informed in an optimistic message:
Should your login and password be available somewhere in the Web, the service will inform you when the entry containing your data has appeared in the Internet:
If your password has appeared on the list, don't panic yet. There is nothing to worry about, provided that you don't use the same password to access numerous accounts. Changing your passwords takes a while, but it's better now than too late, as you will not be unpleasantly surprised in the future. Remember that securing your e-mail account ought to be your No. 1 safety issue, since losing access to your e-mail account may jeopardize your overall safety - e-mail account is like a masterkey.