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| What is a Firewall? SUMMARY: This tip defines a firewall and why it is important for your computer's security.
(This definition of a firewall is NOT complete but meant to provide a basic explanation of the term, mainly to beginning and intermediate computer users.)
A basic definition of a firewall is either a software program or hardware device you can use when connected to a network (such as Internet), mainly to help prevent your machine from getting attacked.
"Attacks" usually occur when an application you are running, or the operating system itself, is vulnerable to problems.
Two examples of the types of vulnerabilities that can occur:
* Your multimedia player cannot handle a specially-crafted audio or video file. When it tries to play the file, the multimedia player may crash, or worse, malicious instructions can be embedded in the file that when read, cause all sorts of problems, including opening a 'back door' on your computer.
* Your operating system, when sent enough requests from a malicious computer on the Internet, could either slow down to a crawl or crash. This is called a denial-of-service attack.
Although operating systems and applications are updated to protect against known vulnerabilities, software designers are not perfect and it is only a matter of time before malicious people find and exploit problems. Firewalls can literally 'close up' known and potential holes on your computer. This helps prevent vulnerabilities, even as-of-yet unknown ones, from being exploited.
Firewalls mainly perform this task in two ways:
* An 'inbound firewall' filters data from an outside network, hopefully preventing all but legitimate information from being sent to your computer.
* An 'outbound firewall' performs the opposite type of filtering. It helps prevent a computer that has been attacked from sending certain types of information to the outside world, announcing that the computer is vulnerable.
The best firewalls do both to help protect your machine.
Firewalls are not perfect and they alone cannot stop your computer from falling victim to malicious activity, but they can greatly lower the chances.
By the way, the term "firewall" comes from the term "fire wall", a wall built inside houses, apartments, or other structures that helps prevent fires from spreading from one room to another. Likewise, a computer "firewall" helps prevent problems on the Internet from spilling onto your computer.
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