Nikto is an Open Source (GPL) web server scanner which performs
comprehensive tests against web servers for multiple items, including
over 6700 potentially dangerous files/programs, checks for outdated
versions of over 1250 servers, and version specific problems on over
270 servers. It also checks for server configuration items such as
the presence of multiple index files, HTTP server options, and will
attempt to identify installed web servers and software. Scan items and
plugins are frequently updated and can be automatically updated.

Nikto is not designed as a stealthy tool. It will test a web server
in the quickest time possible, and is obvious in log files or to an
IPS/IDS. However, there is support for LibWhisker's anti-IDS methods
in case you want to give it a try (or test your IDS system).

Not every check is a security problem, though most are. There are some
items that are "info only" type checks that look for things that may
not have a security flaw, but the webmaster or security engineer may
not know are present on the server. These items are usually marked
appropriately in the information printed. There are also some checks
for unknown items which have been seen scanned for in log files.