This package helps you to install a set of tools to check remote systems, sniff for passwords and more. observe that this kind of activity can be illegal so you have to check if you are authorized to do so in the environment where you install this package.
you can check exploits, sniff for passwords and similar things.
nessus note: you have to have the nessus client installed on some host. the client is provided by the 'nessus' package. you can install it on the same host but that is not necessary.
note! this package includes packages that can damage the system that you audit. it should only be used to audit hosts, networks or systems that you are allowed to audit. i repeat: it can damage the hosts that are checked. you have been warned!