Your Internet-connected computer is probed many times each day by automated attack tools seeking ways to break into and take over your system. Severe attacks may delete important data, crash your system, spawn new attacks or even steal personal information such as passwords and credit card numbers.
A desktop firewall is software that runs directly on a computer (i.e. the host) and protects that host against attack from the network by controlling incoming and/or outgoing network traffic. Sometimes they are referred to as host-based firewalls. Rules govern what data will be blocked or allowed to pass through. For instance, firewalls can block information from machines or ports that are unfamiliar to you.
Both Windows XP and Mac OS X have built-in firewalls. For most users, the default settings of these host-based firewalls are enough, however you should make sure the firewall is enabled for increased protection.
There are other kinds of firewalls that sit on the network between one or more computers and the rest of the network, whose purpose is different than that of host-based firewalls. Use of these firewalls does not necessarily preclude the use of host-based firewalls, based on our campus’s layered security approach.