|| Nessus is a free, powerful, up-to-date and easy to use remote security scanner.
Unlike many other security scanners, Nessus does not take anything for granted. That is, it will not consider that a given service is running on a fixed port - that is, if you run your web server on port 1234, Nessus will detect it and test its security. It will not make its security tests regarding the version number of the remote services, but will really attempt to exploit the vulnerability.
NOTE: Since Nessus 3 is not released under the GPL and is not re-distributable we can not offer it for download.