"A scanner is a program that automatically detects security
weaknesses in a remote or localhost. Scanners are important to
Internet security because they reveal weaknesses in the
"System administrators can strengthen the security of networks
by scanning their own networks. The primary attributes of a scanner
The capability to find a machine or network.
The capability to find out what services are being run on the
host ( once having found the machine).
The capability to test those services for known holes."
"There are various tools available for Linux system scanning and
intrusion detection. I will explain some of the very famous tools
available. I have divided the scanners into three categories: Host
Scanners, Network Scanners, and Intrusion Scanners."