Gatekeeper 1.2.7 is a set of Macintosh system extensions (INITs) and related control panels (cdevs) that, when active (i.e. allowed to install themselves during the boot process), offer protection against attacks by all viruses known to the author at the time of this release.
Gatekeeper also monitors computer activities for what are considered to be suspicious 'events' or 'operations,' in an attempt to intercept what could be variants of known viruses or even completely new viruses.
Since its initial release in January of 1989, Gatekeeper has repeatedly demonstrated its ability to stop the spread of viruses which were unknown during its design. Like any anti-virus system, however, it cannot guarantee complete protection.
Of course, no claims or promises are made regarding Gatekeeper's effectiveness or suitability, and some functions and capabilities of Gatekeeper are non-trivial to use and may require a careful reading of the documentation.
Version 1.2.7 enhances the capabilities of, and corrects bugs in, version 1.2.6. Gatekeeper 1.2.7 is archived at <sumex-aim.stanford.edu> as /info-mac/virus/gatekeeper-127.hqx.
[Recent discussions on the Internet indicate that the previous version of Gatekeeper and AutoDoubler 2.0 from Fifth Generation Systems tended not to agree on various matters. We use John Norstad's excellent and unobtrusive Disinfectant, but early reports indicate that Chris fixed some of the conflicts between the two. -Adam]