What Is a Firewall?
The term firewall has taken on many meanings through the years, and the device we know now as a firewall is the result of a long evolution (keeping in mind that 28 years is a long time in cyberspace).
A firewall is a device that is placed in the network pathway in such a way that it must forward packets for them to reach the network. This might sound like a router; in fact, a firewall doesn’t have to be a router, but firewall functionality is often built into routers. The important distinction is that a conventional router forwards packets when it can—a firewall forwards packets when it wants to. Forwarding decisions are not based solely on addressing but are instead based on rules configured by the network owner regarding ...
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