For many home PC users, their first introduction to firewalls come when they create a problem--a firewall may block some Internet application from running properly or may need to be modified in order to allow a game to run. But while they may cause some hassles, personal firewalls are an indispensable protection for any PC that is connected to a DSL or cable modem.
What a Firewall Does
A firewall is a program that analyzes information as it flows to and from your computer. The earliest firewalls were designed to block any unauthorized access requests to your computer, but more recent firewalls (such as the one built into Windows 7) can also block unauthorized requests traveling from your computer. By blocking unauthorized traffic, the firewall prevents hackers from planting software on your computer without your knowledge. Some of these programs are viruses designed to disable your computer, but others are "bots" that allow hackers to secretly use your computing power for their own purposes.
The Threat to Home PCs
Early firewalls were designed to protect computer networks, which were the first systems to have high-speed Internet connections that were always on. Constant Internet connectivity makes it much easier for a hacker to find and invade a computer, and a computer with a high-speed Internet connection makes a much more desirable platform for bots. Today, most home computers also have always-on Internet connections, thanks to the expanded use of DSL and cable modems. Increasingly, the computers themselves are left on, often downloading and installing updates while their owners sleep. These conditions create the need for firewall protection even for individual computers.
Common Personal Firewalls
Perhaps the most common firewall on PCs is Microsoft Windows Firewall, which became a standard part of the operating system with Windows XP Service Pack 2, and has been build into Windows Vista and Windows 7. Windows Firewall is turned on by default, and generates a notification whenever an outside entity attempts to access your computer. Other common personal firewalls are those included in the Norton Internet Security Suite and Kaspersky Internet Security.
Dealing with Firewall Problems
For all their benefits, personal firewalls can get in the way of the proper functioning programs and web sites. Programs that commonly cause firewalls conflicts include PC games that use Internet access, VOIP applications such as Skype, and some file-sharing programs. However, most firewalls allow you to define a list of websites and programs that have permission to access your computer, so you don't suffer constant interruptions. In some cases, you may need to define "pinholes" in your firewall--definitions of specific communications ports that will be unprotected while being used by certain programs.
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