ABSTRACT
Firewalls act as guards at the computer’s entry points (which are called
ports
) where the computer exchanges data with other devices on the network. They ensure that packets attempting to enter the computer abide by certain rules that have been established by the user of the computer. Firewalls operate in two ways: by either denying or accepting all messages based on a list of designated acceptable (white listed) or unacceptable (blacklisted) sources, or by allowing or denying all messages based on a list of designated acceptable (white listed) or unacceptable (blacklisted) destination ports.
