Password security/Weak Password lockout

[Paul Gupta <wubrgamer@gmail.com>]

By what mechanism does debian decide whether or not a password is too 
weak etc.

I have seen opensuse and perhaps fedora do the same thing during the 
installation.  It'll spit out a warning saying similar to "This password 
is too weak, are you sure you want to use it?"

I'm assuming (which I hate to do, which is why I'm asking) that it's 
using the same thing across all of these different distros.

What is it exactly? AND How would one configure it to be stricter or 
more lenient with password selection?

Thank you!
--
~Paul