Using Nmap to find open ports

Nmap or Network Mapper is a security scanner that was written by Gordon Lyon in September 1997. It is used to find hosts and services in a network. Nmap has various features and scripts that are designed to perform various tests, such as finding the OS, service version, and brute-force default logins.

The following are some of the most common types of scan:

• TCP connect() scan
• SYN stealth scan
• UDP scan
• Ping scan
• Idle scan