The lowdown on firewalls

What is it? A firewall is nothing more or less than a filter that attempts to block data streams you don't want to enter or leave your network. They accomplish this in several ways, including blocking all traffic over some ports. A firewall also can restrict traffic according to originating IP addresses or by constantly monitoring the stream of data and trying to determine which traffic is legitimate and which may be malicious.

Do I need it? If you have a computer with a static IP address, definitely yes. Sooner or later someone will try to penetrate your system'probably within minutes of connecting to the Internet. Any telecommuter probably also needs one, especially if he or she has a cable modem or two-way satellite connection. Mobile workers need one if they are using IEEE 802.11x wireless connections.

When don't I need one? About the only people who don't need firewalls are those with standalone PCs without a modem. In many instances, enterprise network managers or even those managing smaller networks will want to place firewalls between each pair of networks even if they just interconnect and are not linked to the public Web.

Must-know info? Probably the most critical point to remember is that a firewall doesn't offer perfect protection. There are hacker tools designed to bring them down or sneak past them, and they are seldom effective at blocking outgoing traffic generated by malware. Also, there are many instances where widely deployed firewall software has been found to have vulnerabilities that can be exploited by hackers.

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