Firewalls
The computer version of a firewall is a
software program or hardware
device that controls access between two networks, such as a local area network and the Internet or the
Internet and a
computer.
A port on a computer is like a door; it permits traffic to leave and enter a computer.
When the port is closed, traffic cant leave or enter the computer.
A port scan occurs when one computer tests all or some of the ports of another computer to determine whether its ports
are open, or closed.