Blocking Attacks by Using a Firewall

Many of the dire events we discuss in this book can be prevented by using a properly configured firewall. (Properly configured personal firewall software can protect a computer from any outside attack, whether it originates from the Internet or from another computer on the same network. Network-based firewall devices are usually designed to protect computers inside the firewall—those on the same network segment—from threats that originate from the Internet. The combination can provide a level of security that is extremely effective.) As shown in Figure 1-2 a firewall prevents entry of packets that don't meet the criteria you specify, while allowing transparent passage to authorized connections.

Figure 1-2. A ...

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