During a security assessment, an administrator wishes to see which services are running on a
remote server. Which of the following should the administrator use?

A.
Port scanner

B.
Network sniffer

C.
Protocol analyzer

D.
Process list

Explanation:
Different services use different ports. When a service is enabled on a computer, a network port is
opened for that service. For example, enabling the HTTP service on a web server will open port 80
on the server. By determining which ports are open on a remote server, we can determine which
services are running on that server.
A port scanner is a software application designed to probe a server or host for open ports. This is
often used by administrators to verify security policies of their networks and by attackers to identify
running services on a host with the view to compromise it.
A port scan or portscan can be defined as a process that sends client requests to a range of
server port addresses on a host, with the goal of finding an active port. While not a nefarious
process in and of itself, it is one used by hackers to probe target machine services with the aim of
exploiting a known vulnerability of that service. However the majority of uses of a port scan are not
attacks and are simple probes to determine services available on a remote machine.