this section covers the basics of network scanning with nmap

This section covers the basics of network scanning with Nmap. Before we begin it is important to understand the following concepts:

- Firewalls, routers, proxy servers, and other security devices can skew the results of an Nmap scan. Because of this, scanning remote hosts that are not on your local network may produce misleading information.

- Some scanning options require elevated privileges. On Unix and Linux systems you may be required to login as the root user or to execute Nmap using the sudo command.

There are also a couple of warnings to take into consideration:

- Scanning networks that you do not have permission to scan can get you in trouble with your internet service provider, the police, and possibly even the government. Don’t scan the FBI or Secret Service websites unless you want to get in trouble.

- Aggressively scanning some systems can lead to undesirable results such as system downtime or data loss. Always scan mission critical systems with caution.

Now let’s start scanning!

Scan a Single Target

Executing Nmap with no command line options will perform a basic scan on the target system. A target can be specified as an IP address or host name (which Nmap will try to resolve).

Usage syntax: nmap [target]