Guidelines on choosing passwords and keeping them safe.

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Password Guidelines

Keep it secret, Keep it safe
Choosing the right password is something that many people find difficult, there are so many things that require passwords these days that remembering them all can be a real problem. Perhaps because of this a lot of people choose their passwords very badly. The simple tips below are intended to assist you in choosing a good password.
I'm also starting work on a Password FAQ, which will probably replace this document.
See also my password recovery speeds page, which lists the time taken to break various passwords using brute force alone.
Basics

• Use at least eight characters, the more characters the better really, but most people will find anything more than about 15 characters difficult to remember.
• Use a random mixture of characters, upper and lower case, numbers, punctuation, spaces and symbols.
• Don't use a word found in a dictionary, English or foreign.
• Never use the same password twice.

Things to avoid

• Don't just add a single digit or symbol before or after a word. e.g. "apple1"
• Don't double up a single word. e.g. "appleapple"
• Don't simply reverse a word. e.g. "elppa"
• Don't just remove the vowels. e.g. "ppl"
• Key sequences that can easily be repeated. e.g. "qwerty","asdf" etc.
• Don't just garble letters, e.g. converting e to 3, L or i to 1, o to 0. as in "z3r0-10v3"

Tips

• Choose a password that you can remember so that you don't need to keep looking it up, this reduces the chance of somebody discovering where you have written it down.
• Choose a password that you can type quickly, this reduces the chance of somebody discovering your password by looking over your shoulder.

Bad Passwords

• Don't use passwords based on personal information such as: name, nickname, birthdate, wife's name, pet's name, friends name, home town, phone number, social security number, car registration number, address etc. This includes using just part of your name, or part of your birthdate.
• Don't use passwords based on things located near you. Passwords such as "computer", "monitor", "keyboard", "telephone", "printer", etc. are useless.
• Don't ever be tempted to use one of those oh so common passwords that are easy to remember but offer no security at all. e.g. "password", "letmein".
• Never use a password based on your username, account name, computer name or email address.

Choosing a password

• Use good password generator software.
• Use the first letter of each word from a line of a song or poem.
• Alternate between one consonant and one or two vowels to produce nonsense words. eg. "taupouti".
• Choose two short words and concatenate them together with a punctuation or symbol character between the words. eg. "seat%tree"

Changing your password

• You should change your password regularly, I suggest once a month is reasonable for most purposes.
• You should also change your password whenever you suspect that somebody knows it, or even that they may guess it, perhaps they stood behind you while you typed it in.
• Remember, don't re-use a password.

Protecting your password

• Never store your password on your computer except in an encrypted form. Note that the password cache that comes with windows (.pwl files) is NOT secure, so whenever windows prompts you to "Save password" don't.
• Don't tell anyone your password, not even your system administrator
• Never send your password via email or other unsecured channel
• Yes, write your password down but don't leave the paper lying around, lock the paper away somewhere, preferably off-site and definitely under lock and key.
• Be very careful when entering your password with somebody else in the same room.

Remembering your password

Remembering passwords is always difficult and because of this many people are tempted to write them down on bits of paper. As mentioned above this is a very bad idea. So what can you do?

• Use a secure password manager, see the downloads page for a list of a few that won't cost you anything.
• Use a text file encrypted with a strong encryption utility.
• Choose passwords that you find easier to remember.

Bad Examples

• "fred8" - Based on the users name, also too short.
• "christine" - The name of the users girlfriend, easy to guess
• "kciredref" - The users name backwords
• "indescribable" - Listed in a dictionary
• "iNdesCribaBle" - Just adding random capitalisation doesn't make it safe.
• "gandalf" - Listed in word lists
• "zeolite" - Listed in a geological dictionary
• "qwertyuiop" - Listed in word lists
• "merde!" - Listed in a foreign language dictionary

Good Examples

None of these good examples are actually good passwords, that's because they've been published here and everybody knows them now, always choose your own password don't just use somebody elses.

• "mItWdOtW4Me" - Monday is the worst day of the week for me.

How would a potential hacker get hold of my password anyway?

There are four main techniques hackers can use to get hold of your password:

1. Steal it. That means looking over your should when you type it, or finding the paper where you wrote it down. This is probably the most common way passwords are compromised, thus it's very important that if you do write your password down you keep the paper extremely safe. Also remember not to type in your password when somebody could be watching.
2. Guess it. It's amazing how many people use a password based on information that can easily be guessed. Psychologists say that most men use 4 letter obscenities as passwords and most women use the names of their boyfriends, husbands or children.
3. A brute force attack. This is where every possible combination of letters, numbers and symbols in an attempt to guess the password. While this is an extremely labour intensive task, with modern fast processors and software tools this method is not to be underestimated. A Pentium 100 PC might typically be able to try 200,000 combinations every second this would mean that a 6 character password containing just upper and lower case characters could be guessed in only 27½ hours.
4. A dictionary attack. A more intelligent method than the brute force attack described above is the dictionary attack. This is where the combinations tried are first chosen from words available in a dictionary. Software tools are readily available that can try every word in a dictionary or word list or both until your password is found. Dictionaries with hundreds of thousands of words, as well as specialist, technical and foreign language dictionaries are available, as are lists of thousands of words that are often used as passwords such as "qwerty", "abcdef" etc.