A internet hacker posted a list of username/passwords of 450,000 Yahoo! accounts to the internet after exploiting a breach in security.

If you have a Yahoo! account, the complete list of usernames can be found here so that you can check for your username. Just type your username into the search and it will come up for you.

The hacker, which calls itself "D33Ds," claims it hacked into the online giant's (NASDAQ: YHOO) database by using an easy hacker trick. However, the company said that fewer than 5 percent of the accounts posted were valid Yahoo accounts.Stories like this are a great reminder to make "difficult" passwords for your emails and personal accounts. Never use passwords like "12345" or "password".

Experts on the web agree that safer passwords to use have both uppercase and lowercase letters, are longer in length and that you use a different password for each account you have. You should NOT USE:

  • Your name
  • Your spouse's name
  • Your parent's name
  • Your pet's name
  • Your child's name
  • Names of close friends or coworkers
  • Names of your favorite fantasy characters
  • Your boss's name
  • Anybody's name
  • The name of the operating system you're using
  • The hostname of your computer
  • Your phone number
  • Your license plate number
  • Any part of your social security number
  • Anybody's birth date
  • Other information that is easily obtained about you
  • Words such as wizard, guru, gandalf, and so on.
  • Any username on the computer in any form (as is, capitalized, etc.)
  • A word in the English dictionary
  • A word in a foreign dictionary
  • A place
  • A proper noun
  • Passwords of all the same letter
  • Simple patterns on the keyboard, like qwerty
  • Any of the above spelled backwards
  • Any of the above followed or prepended by a single digit

Hope this helps!