Port scanner

A port scanner is a software used for checking open ports on a system. This software is often used by administrators to ensure the security of the system. Attackers also use this types of software to collect valuable information from the system so that they can compromise it.

Port scanner works by sending a connection initiation request and by studying the response of it. If multiple systems are port scanned for a particular open port, it is called port sweeping. For example, HTTP web servers running on a network can be found out by looking for systems that listens on port 80.