From LQWiki

Nmap ("Network Mapper") is a well-known utility for network exploration or security auditing. It is distributed under the GPL. It can rapidly scan a large network using raw IP packets "in novel ways" to give feedback about which hosts are active, which OS they are running, which ports/services are open and awaiting connections, etc., etc., ad infinitum.

Tips

(Some options require root-privelages.)

• Here's a pretty thorough scan recipe:

nmap -T Aggressive -P0 -sT -p 1-65535 <insert host IP here>

• There is also nmapfe, which is a GUI frontend for nmap

Examples

• This command will scan your system for open ports

nmap localhost

• This command will see if the default svn port (6963) is open on your system:

nmap localhost -p 6963

• This command will print a list of common options

nmap -h

See also

• Linux security vulnerabilities
• netstat

External links

• Nmap home page (www.insecure.org)
• Nmap docs (www.insecure.org)