Early 90s Mac freeware anti-virus program

Solution 1:

Disinfectant was a popular freeware antivirus program on the Mac from the 80's until its official retirement at version 3.7.1 in 1998:

Announcement and Press Release May 6, 1998 Updated: October 11, 1998 I regret to announce that I am officially retiring Disinfectant, our free anti-viral utility for the Macintosh. The current version 3.7.1 is the last version. Disinfectant will not be updated for the new Autostart 9805 worm or for any future viruses, worms, or other Macintosh malware.

It's the last antivirus I've used on my Macs. There hasn't been much need.