18.104.22.168. Scanning Hosts with Nmap
Nmap is a popular tool that can be used to determine the layout of a network. Nmap has been available for many years and is probably the most often used tool when gathering information. An excellent manual page is included that provides detailed descriptions of its options and usage. Administrators can use Nmap on a network to find host systems and open ports on those systems.
Nmap is a competent first step in vulnerability assessment. You can map out all the hosts within your network and even pass an option that allows Nmap to attempt to identify the operating system running on a particular host. Nmap is a good foundation for establishing a policy of using secure services and restricting unused services.
Nmap can be run from a shell prompt by typing the
nmap command followed by the host name or IP address of the machine to scan:
nmap <host name>
For example, to scan a machine with host name
foo.example.com, type the following at a shell prompt:
The results of a basic scan (which could take up to a few minutes, depending on where the host is located and other network conditions) look similar to the following:
Interesting ports on foo.example.com:
Not shown: 1710 filtered ports
PORT STATE SERVICE
22/tcp open ssh
53/tcp open domain
80/tcp open http
113/tcp closed auth
Nmap tests the most common network communication ports for listening or waiting services. This knowledge can be helpful to an administrator who wants to close down unnecessary or unused services.
For more information about using Nmap, see the official homepage at the following URL: