DIRB is a Web Content Scanner. It looks for existing (and/or hidden)
Web Objects. It basically works by launching a dictionary based attack
against a web server and analizing the response.

DIRB comes with a set of preconfigured attack wordlists for easy usage
but you can use your custom wordlists. Also DIRB sometimes can be used
as a classic CGI scanner, but remember it is a content scanner not a
vulnerability scanner.

DIRB main purpose is to help in professional web application auditing.
Especially in security related testing. It covers some holes not
covered by classic web vulnerability scanners. DIRB looks for specific
web objects that other generic CGI scanners can't look for. It doesn't
search vulnerabilities nor does it look for web content that could be
vulnerable.