Firewalls
Firewalls are policy based filtering systems (composed of both hardware and software) which control and restrict the flow of data between networked computer systems. Firewalls establish a physical or logical perimeter where selected types of network traffic may be blocked. Blocking policies are typically based on computer IP addresses or protocol type of application (e.g. web access or file transfer).

Firewall Machine
A dedicated gateway computer with special security precautions on it, used to service outside network, especially Internet, connections and dial-in lines. The idea is to protect a cluster of more loosely administered machines hidden behind it from intrusion. The typical firewall is an inexpensive microprocessor-based Unix machine with no critical data, with modems and public network ports on it, but just one carefully watched connection back to the rest of the cluster. The special precautions may include threat monitoring, call-back, and even a complete iron box which can be keyed to particular incoming IDs or activity patterns.

Firewall Code
The code put in a system (say, a telephone switch) to make sure that the users can't do any damage. Since users always want to be able to do everything but never want to suffer for any mistakes, the construction of a firewall is a question not only of defensive coding but also of interface presentation, so that users don't even get curious about those corners of a system where they can burn themselves.

Firmware
A sort of 'halfway house' between Hardware and Software. Firmware often takes the form of a device which is attached to, or built into, a computer - such as a ROM chip - which performs some software function but is not a program in the sense of being installed and run from the computer's storage media.

Fix
An operational expedient that may be necessary if there is an urgent need to amend or repair data, or solve a software bug problem.

Frame Relay
A method of communication that incrementally can go from the speed of an ISDN to the speed of a T1 line. Frame relay has a flat-rate billing charge instead of a per time usage charge. Frame relay connects via a telephone company's network.

Freeware
Literally, software provided for free - no charge. This is not as uncommon as might be expected. Major software developers often give away old versions of their products to allow users to try them at no charge and, hopefully, succeed in tempting them to purchase the current release. Independent developers may give away small programs to establish a reputation for useful software, which then enables them to charge. Cover disks attached to a computer magazine often contain Freeware. As with Shareware, Freeware should be approached with caution, and staff dissuaded from trying out their new Freeware on organization equipment.

Freeze / Hang
When an application 'freezes', or 'hangs,' it no longer accepts any input, whether from the keyboard or the mouse. Occasionally, a frozen application will return to normal: the problem may have been related to (say) a disk write command that did not execute, resulting in an time out, but with control retuned to the user. Applications which freeze may also crash the operating system, especially of a PC. However, the latest release of Windows® (the Millennium Edition) resolves this problem. Freezes followed by the need to re-boot and the possible loss of all current data are becoming less common.