06.01
Adi Parmono
Nmap ("Network Mapper") is an open source tool for network exploration and security auditing. It was designed to examine a large network quickly, although it can also work against single hosts. Nmap uses raw IP packets in a sophisticated way to determine which hosts are available on the network, what services (application name and version) of what is given, the operating system (and version) they are running, what type of packet filters / firewalls are in use, and a number of other characteristics. While Nmap is commonly used for security audits, many systems and network administrators find it useful for routine tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime.
The output from Nmap is a list of scanned targets, with supplemental information depending on the options used. Key among that information is "interesting ports table". The table lists the port number and protocol, service name, and status. The state is open (open), filtered (filtered), closed (closed), or not be filtered (unfiltered). Open means that an application on the target machine is listening (listening) for connections / packets on that port. Filtered means that a firewall, filter, or other network obstacle is blocking the port so that Nmap can not tell whether he was open or closed. Closed ports have no application listening on them, although they can be open at any time. Ports are classified as unfiltered when they respond to Nmap probes, but Nmap can not determine whether they are open or closed. Nmap reports the state combinations open | filtered and closed | filtered when it can not determine which describe a port. The port table may also include software version details when asked to do a version. When an IP protocol scan is requested (-sO), Nmap provides information on supported IP protocols rather than the ports in the listening.
In addition to the interesting ports table, Nmap can provide further information on targets, including reverse DNS names, operating system forecasts, type of device, and MAC address.
Nmap scan is shown in Example 1. The argument used in this example is just-A, to check the operating system and version, checking scripts, and traceroute;-T4 for faster execution, and two target hostnames.
The output from Nmap is a list of scanned targets, with supplemental information depending on the options used. Key among that information is "interesting ports table". The table lists the port number and protocol, service name, and status. The state is open (open), filtered (filtered), closed (closed), or not be filtered (unfiltered). Open means that an application on the target machine is listening (listening) for connections / packets on that port. Filtered means that a firewall, filter, or other network obstacle is blocking the port so that Nmap can not tell whether he was open or closed. Closed ports have no application listening on them, although they can be open at any time. Ports are classified as unfiltered when they respond to Nmap probes, but Nmap can not determine whether they are open or closed. Nmap reports the state combinations open | filtered and closed | filtered when it can not determine which describe a port. The port table may also include software version details when asked to do a version. When an IP protocol scan is requested (-sO), Nmap provides information on supported IP protocols rather than the ports in the listening.
In addition to the interesting ports table, Nmap can provide further information on targets, including reverse DNS names, operating system forecasts, type of device, and MAC address.
Nmap scan is shown in Example 1. The argument used in this example is just-A, to check the operating system and version, checking scripts, and traceroute;-T4 for faster execution, and two target hostnames.
For more details, please download the following Nmap tutorial. Download
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