CrackLib tests passwords to determine whether they match certain
security-oriented characteristics, with the purpose of stopping users
from choosing passwords that are easy to guess. CrackLib performs
several tests on passwords: 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; and 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 will also want to install the cracklib-dicts package.