CrackLib tests passwords to determine whether they match certain
security-oriented characteristics. You can use CrackLib to stop
users from choosing passwords which would be easy to guess. CrackLib
performs certain tests:

* It tries to generate words from a username and gecos entry and
checks those words against the password;
* It checks for simplistic patterns in passwords;
* It checks for the password in a dictionary.

CrackLib is actually a library containing a particular
C function which is used to check the password, as well as
other C functions. CrackLib is not a replacement for a passwd
program; it must be used in conjunction with an existing passwd
program.

Install the cracklib package if you need a program to check users'
passwords to see if they are at least minimally secure. If you
install CrackLib, you'll also want to install the cracklib-dicts
package.