Norman ThunderByte Virus Control for DOS/Windows 3.xv8.11 Description:
It has a background scan option which periodically scans your system for viruses, even while other applications are running. A File I/O Monitor automatically scans every file you copy, extract, modify, download, etc. The Integrity Checking feature can warn you when files have been altered. Features include: a heuristic mode for identifying unknown viruses, log files, various scanning options, the ability to delete infected files, and more.