Simply put it acts as a barrier between your computer and the internet. To protect you from crackers, hackers and malware.

If your running DSL or a cable modem you should employ a firewall, as having a direct connection to the Internet can make you a target to attack.

Firewalls can be hardware or software based. With firewalls you set up ACL's or Access Control lists to allow or deny traffic.

There are three different ways a firewall can block traffic.

1. Packet Filtering- Packets are analyzed against filters in the firewall rulesets. Firewalls will drop packets that are not allowed in the firewall rulesets.

2. Proxy Service- Information from the Internet is grabbed by the firewall and delivered to the requesting service thru the proxy.

3. Statefull packet inspection- looks up criteria against a database of trusted information. To see if the packet contains anything that would allow or deny it into the network.

Firewalls are customizable allowing you to create your own rulesets you can block IP addresses, specific protocols such as Telnet, FTP, ICMP, UDP, SMTP and many others.

Firewalls can be customized to block specific ports, or even keywords.

By Benjamin Hargis

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