Using this software is generally not recommended for two reasons: The most recent update is over a decade old and so it does not successfully detect a lot of newer malware, and using the software tends to create CHKLIST.MS files in every scanned directory. This may mean modifying files if the files are treated like folders, which is what may happen when using “Microsoft Compressed Folders” (for some versions of Microsoft Windows) which allows zip files to be treated very similar to folders.
MSAV article makes a few interesting statements: The "Detect and
Clean" process could scan for and detect 1,234 distinct viruses. The
one virus update brought protection up to 2,371 viruses. Microsoft
Anit-Virus for Windows determined that the upgrade to Windows 95 was a
virus, embarrassing Microsoft.
"last virus definitions update for Microsoft Anti-Virus" dated June 1, 1996:
F-Secure's Free Virus Removal Tools refers to F-Secure's FTP site: Anti-Virus/Free section. The Free F-Secure software FAQ refers to F-PROT. F-Secure "228b" from the 286 directory. The software itself has become years old, so the FTP site's updates/ directory (zipped Dec 26, 2007 locally as fsdosupd.zip) should also be obtained. "Only the DOS version of F-Secure Anti-Virus is free. The other versions are either for 30 days-evaluation or commercial ones."
As for F-PROT, http://www.f-prot.com/products/home_use/dos/ no longer says the product is available, but an old forum post linked to F-Prot for DOS (saying it is version 3.16b). AV Defs Updater for (Windows, that updates) F-PROT for DOS (version 2.95 zipped locally at 45% compression ratio) seems to be from a third party and designed to help keep the DOS version of F-PROT updated.