(for home use) program that acts as a Firewall
on Windows 9x/NTx desktops. Is extremely easy to use and configure, as there are few settings to tweak. In the default mode, it will all but lock down
your computer, allowing no access in, and limited access out.
ZoneAlarm's local protection forces each program to be granted permission to access the Internet. This is annoying in some respects, as when some applications and games run in full screen mode, and try to access the Internet, they'll appear to hang, and the machine will appear to lock up, when in actuality ZoneAlarm has blocked the program from accessing the Internet. This can be remedied by pressing alt-y at this time.
By default, ZoneAlarm runs the computer in a "stealth mode", if traffic is directed at any of the ports on a computer with ZoneAlarm running, the computer will not give a response, unless a program is running, and has ZoneAlarm's permission to act as a server.
An extremely useful program -- well worth the price, or lack thereof. The lack of configurability may leave something to be desired.