User guide

Password Security
25
• Your name
• The names of pets
• The names of family members
• Any birth dates
• Your phone number or zip code
• Do Not Invert Recognizable Words — Good password checkers always reverse common words, so
inverting a bad password does not make it any more secure.
Some insecure examples include the following:
• R0X4H
• nauj
• 9-DS
• Do Not Write Down Your Password — Never store a password on paper. It is much safer to
memorize it.
• Do Not Use the Same Password For All Machines — It is important to make separate passwords for
each machine. This way if one system is compromised, all of your machines are not immediately at
risk.
The following guidelines will help you to create a strong password:
• Make the Password at Least Eight Characters Long — The longer the password, the better. If using
MD5 passwords, it should be 15 characters or longer. With DES passwords, use the maximum
length (eight characters).
• Mix Upper and Lower Case Letters — Red Hat Enterprise Linux is case sensitive, so mix cases to
enhance the strength of the password.
• Mix Letters and Numbers — Adding numbers to passwords, especially when added to the middle
(not just at the beginning or the end), can enhance password strength.
• Include Non-Alphanumeric Characters — Special characters such as &, $, and > can greatly
improve the strength of a password (this is not possible if using DES passwords).
• Pick a Password You Can Remember — The best password in the world does little good if you
cannot remember it; use acronyms or other mnemonic devices to aid in memorizing passwords.
With all these rules, it may seem difficult to create a password that meets all of the criteria for good
passwords while avoiding the traits of a bad one. Fortunately, there are some steps you can take to
generate an easily-remembered, secure password.
2.1.3.1.1. Secure Password Creation Methodology
There are many methods that people use to create secure passwords. One of the more popular
methods involves acronyms. For example:
• Think of an easily-remembered phrase, such as:
"over the river and through the woods, to grandmother's house we go."