(There's no video for Gatekeeper yet. Please contribute to MR and add a video now!)
Gatekeeper is a program designed to continuously monitor the operation of your Macintosh, watching for operations that are commonly carried out by viruses as they attempt to spread. When Gatekeeper detects an infection attempt it will automatically stop the attempt, almost before it's started.
This type of monitoring and protection is possible because viruses generally depend on a small group of operations which they use in somewhat unusual ways. Of course, if detecting virus operations was really as straightforward as all that, everyone would be doing it. The fact is there's a catch. Not a big one, but a catch just the same:
Some perfectly normal programs carry out some of the same basic operations
Gatekeeper deals with these "false-alarms" by allowing you to tell it what virus-like operations any given program should be allowed to carry out. You tell Gatekeeper just once, then forget about it - everything's automatic from then on.
Gatekeeper-1.3-distribution.sit (225.47 KiB / 230.88 KB)
Gatekeeper v1.3 (1993) / compressed w/ Stuffit
Gatekeeper1-2.3.sit (98.9 KiB / 101.27 KB)
Version 1.2.3 (1992) / compressed w/ Stuffit
GateKeeper1.1.sit (77.57 KiB / 79.43 KB)
Version 1.1.1 (1989) / compressed w/ Stuffit
Mac OS 4.1 - Mac OS 7.6
Emulating this? It should run fine under: Mini vMac