USING NESSUS TO SCAN YOUR SYSTEM

The best way to know what potential attackers may do to your system is to see what they see. This means getting your hands somewhat dirty and using the tools they use. Most attackers will first probe your system to determine what services you have available and to see if known exploits will work against them.

One popular tool, with both crackers and system admins alike, is Nessus. Nessus is a security scanner that builds upon the excellent port scanner Nmap. Nmap scans a remote host's ports to see what is currently running and tries to make intelligent guesses as to the service that may be listening to a particular port. Nessus takes it one step further.

http://www.nessus.org/
http://www.nmap.org/

Nessus not only uses Nmap to scan for open ports, it also tries to identify services running on the host. It attempts to extract the version of the software and to run some common probes on it to determine if it is vulnerable to any known exploits.

Nessus is an extremely comprehensive scanner that is updated frequently. It tests Web server CGI scripts for common vulnerabilities and runs tests against many other servers. (Some tests Nessus runs, however, can be potentially damaging so it gives you the option of enabling only "safe" plug-ins to avoid accidental system damage.)