CrackLib is a library containing a C function (well, lots of functions
really, but you only need to use one of them) which may be used in a
"passwd"-like program.

The idea is simple: try to prevent users from choosing passwords that
could be guessed by "Crack" by filtering them out, at source.

CrackLib is an offshoot of the the version 5 "Crack" software, and
contains a considerable number of ideas nicked from the new software.