Firewall software is primarily a security measure, forming a virtual checkpoint to protect computers and other network devices from attack. However, increased network security is not the only benefit that firewall software can confer. Firewalls can also be used to help enforce rules regarding network use in the home or office, as well as helping you to monitor the activity on your network.
How Firewalls Work
Firewalls use rules to examine network packets as they pass through a particular location on a network. If a packet does not contravene any of the firewall's rules, the firewall will allow the packet through to its destination. However, a packet that breaks a firewall rule -- for example, by originating from a host that has been blocked from sending traffic to the network -- will be discarded.
Firewalls provide markedly increased security for computers and other devices, especially on networks that are connected to the Internet. Without firewall software, it would be very easy for attackers to send malicious programs to your computer over a network, drastically increasing the load on your computer's anti-virus and anti-malware programs. With a firewall in place, however, you can dictate exactly what the computers on your network are able to send and receive from the outside world, helping you to cut threats off at their source.
Monitoring With Firewalls
Firewall logging is the process of monitoring network traffic through a firewall. By definition, firewalls need to examine network packets closely as those packets pass by. Some firewalls can compile logs using the information that they gain from these packets, noting parameters such as the packet's destination, source and size. These logs can then be used to help determine network conditions, including which areas of the network are busiest and which network applications consume the most data.
Many networks have policies regarding which users can access data. For example, a school would likely prevent all of its computers from accessing adult content, while a home user might limit the amount of time that her children could use the Internet. Firewalls allow users to actively enforce these policies by creating specific rules. As such, the school might create a firewall rule blocking all content containing certain keywords, while the home user might create a rule blocking all Internet traffic from her children's computer user accounts, except at specific times.
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