"There are a number of security scanners out there.
Most of them are vendor specific, and each boasts a number of
vulnerability checks to determine what is secure on your system and
what is not. So what if you are a hardcore open source paranoid
like myself who wouldn't think to spend a dime on the latest
commercial security scanner from CyberSlueths or CrackerCops? Well
there is a superior alternative that is regularly updated, free,
and open source. It's called Nessus, and it is by far the best