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In computer security, Nessus is a free comprehensive vulnerability scanning software. Its goal is to detect potential vulnerabilities on the tested systems. For example:

* Vulnerabilities that allow a remote cracker to control or access sensitive data on a system. * Misconfiguration (e.g. open mail relay, missing patches, etc). * Default passwords, a few common passwords, and blank/absent passwords on some system accounts. Nessus can also call Hydra (an external tool) to launch a dictionary attack. * Denials of service against the TCP/IP stack.

On UNIX (including Mac OS X), it consists of nessusd, the Nessus daemon, which does the scanning, More >