Culture website BoingBoing has published a great article explaining how passwords can get cracked. Lot’s of easy to understand examples and best practices to keep you safe.
A typical password consists of a root plus an appendage. The root isn’t necessarily a dictionary word, but it’s usually something pronounceable. An appendage is either a suffix (90% of the time) or a prefix (10% of the time). One cracking program I saw started with a dictionary of about 1,000 common passwords, things like “letmein,” “temp,” “123456,” and so on. Then it tested them each with about 100 common suffix appendages: “1,” “4u,” “69,” “abc,” “!,” and so on. It recovered about a quarter of all passwords with just these 100,000 combinations.
Crackers use different dictionaries: English words, names, foreign words, phonetic patterns and so on for roots; two digits, dates, single symbols and so on for appendages. They run the dictionaries with various capitalizations and common substitutions: “$” for “s”, “@” for “a”, “1” for “l” and so on. This guessing strategy quickly breaks about two-thirds of all passwords.
Choosing A Secure Password