Network Service Scanning is the process of discovering services on networked systems. This can be achieved through a technique called port scanning or probing. Port scanning interacts with the TCP/IP ports on a target system to determine whether ports are open, closed, or filtered by a firewall. This does not reveal the service that is running behind the port, but since many common services are run on [https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml specific port numbers], the type of service can be assumed. More in-depth testing includes interaction with the actual service to determine the service type and specific version. One of the most-popular tools to use for Network Service Scanning is [https://nmap.org/ Nmap].