How complex does a password have to be in order to provide a sense of security? The answer to this question really depends on the possible characters that comprise the password, and how many characters the password contains.

If you only use the 26 characters of the English alphabet and your password is only 2 characters long, then you have only 676 (26 to the power of 2) possible passwords. A password-cracking computer program can guess any password of this length that you create from two letters in a fraction of a second.

If you choose your password from both lowercase and uppercase characters, numbers, the ten number keys, and the 32 special characters on your keyboard, such as the comma and the asterisk, then the number of distinct passwords increases to 9,216 (96 to the power of 2), which is still a low number.

However, if you make sure that the password consists of at least 7 characters, then the number of possible combinations increases to over 75 trillion, or to be exact -- 75,144,747,810,816 (96 to the power of 7). It would take a hacker over 2,300 years to try every possible combination if the password-cracking program tried 1,000 possible passwords every second.

Using a very powerful computer that tried one million passwords every second, it would still take 2.3 years. If you change your password every month or two, the password will most likely be different by the time the hacker has cracked it.