A good firewall definition is one that clearly identifies what it is and how it works. A firewall is simply a proxy device (running either hardware or software on the system) that lies between the computer and the network. It acts as a protective system to filter traffic in order to protect the data between networks less trustworthy.

Basically, the concept of a firewall really reflects how such a programmable device can protect Internet-connected computers from security threats and attacks. It is up to users to configure and setup the firewall parameters to ensure all network traffic is channeled so an attacker will not compromise data.

Another appropriate firewall definition explains how such a device can screen traffic before it allows traffic to enter a protected network. The firewall will either accept or reject Internet traffic going into and out of computers on the basis of their IP addresses and ports. What takes place is, the firewall acts as a service to ensure the validity of inside addresses; thus, to protect resources from intruders or hackers.

Ultimately, a good firewall definition states that it is an application program that is used by the computer users to block unwanted traffic. It also explains how it works as a guard and is capable of generating logs of accesses.

More about firewalls and how it can enable IPsec on a local area network can be read at the URL http://nucleonet.com. It explains how firewalls are put into practice and incorporated into security appliances.