In the real world, "Fire Wall" is a fire-retardant wall meant to deter the spread of fire from one section to another. One example of it is a wall separating a car engine from the passenger compartment.
In computers, it is a device, hardware or software, meant to merely monitor, restrict, and/or filter, outside accesses from a network and therefore aid user security. Firewalls try to prevent attacks, exploits, etc. to ensure computer operators retain their privacy. Since a firewall can pay close attention to incoming and outgoing connections, it can often be a key component in getting rid of spyware or getting rid of spam.
Many system administrators do not use firewalls for their systems, opting instead to close off unnecessary ports and services on a server. Since many users are not able to do this effectively, a firewall is often useful for both Windows and Linux systems (included in RedHat and other distributions by default).
Windows XP has a very basic firewall available in the Network properties "Advanced" tab. Users are encouraged to use a full firewall such as McAfee, Norton, or ZoneAlarm. For a list of other software firewalls: Firewall-Software.com. Firewalls need accurate configuration or they become mostly useless.
Note: NAT routers are not firewalls but are marketed as such.
- PC-Help: What is a firewall?
- Firewall-Software.com - FAQ: What is a firewall?
- More Firewall software
- A list of firewalls - some free, some not - compared.
- AntiFirewall - a shareware tool to help overcome firewalls that sometimes are too secure, placing restrictions on user's activity.
- TCPView - a program that watches incoming and outgoing connections, similar to a firewall but without any automatic restrictions.