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Microsoft Antivirus (or MSAV) was an antivirus program for MS-DOS. The first version of MSAV came with was MS-DOS 6.1. It is accessed by typing "MSAV" in the command prompt, and able to detect around 1,234 viruses. It first appeared in MS-DOS version 6.0. It had a Windows 3.1 counterpart, MSAVW (Microsoft Antivirus for Windows). It was supplied by Central Point Software Inc. which was later bought by Symantec in 1994, which later helped design and program Norton Antivirus.

It was one of the only antiviruses on MS-DOS, meaning that if the user doesn't have it, or doesn't know about it, they might not be able to remove a virus off of the computer.

Although it is discontinued in NT-based Windows versions, Microsoft-made antivirus programs like Windows Defender and Microsoft Security Essentials for the later NT-based Windows.

On MS-DOS versions 6.0 to 6.22, it was a default program, and it had no cursor, meaning the user had to navigate by using the arrow keys. On China DOS Union's MS-DOS 7.1, it was able to be installed by the add-on installer in the MS-DOS 7.1 setup, this version of the antivirus had a cursor, meaning if the user has a mouse, the user can navigate using the cursor instead of the arrow keys.


The program could detect and clean, and scan different drives. It also had an anti-stealth and checksum feature that could be used to detect changes in normal files, which was to make up for the fact that it cannot update. The final version added the ability to check for polymorphic viruses, increasing the virus detection to 2,371 viruses in total.


VSafe was a terminate-and-stay-resident (TSR) component of MSAV that had real-time virus detection. It is accessed by typing "VSafe TSR" in the prompt. It can be turned off by pressing Alt-V and then pressing Alt-U.

VSafe does the following:

  • Checks executable files for viruses
  • Checks all disks, including hard drives and floppy disks for boot sector viruses.
  • Warns the user of virus attempts to overwrite the boot sector of the hard disk.
  • Warns about formatting a drive, which could erase the hard drive.

VSafe had a number of virus definitions embedded within the file, however it could delete these viruses and it was capable of loading additional signatures (updates) from an external definition file.


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