How do scanners work?

What will be an ideal response?

Scanners automate the process of examining network weaknesses. Scanners are not heuristic; they do not discover new vulnerabilities but check for known vulnerabilities and open ports. A scanner performs these functions:* Connects to a target host(s)* Examines the target host for the services running on it* Examines each service for any known vulnerability?Scanners can be set to target either a single IP address,and search for vulnerabilities on the target host, or a range of IP addresses. In either mode, the scanner attempts to connect with the target (or targets) to find open ports and possible vulnerabilities present on the target host(s).