How does a Firewall Work?

A firewall monitors incoming and outgoing network traffic and decides whether to allow or block the traffic. It uses a preset list of security rules to make decisions, and then it will establish a barrier between your internal network, which is secured, controlled and trusted, and the outside networks, such as the Internet. Using a firewall is the single most effective method for protecting your computer from becoming infected with viruses, worms and hackers.
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