F-Secure Virus Descriptions : Zero Bug

The "Zero Bug" will mark infected files in the same way as the Vienna virus, placing 62 in the "seconds" field of the timestamp of the .COM files it infects. Apart from this, the viruses are very dissimilar.

This virus will search for COMMAND.COM, using the value of the COMSPEC environment variable to locate the file. Then it will remain resident, hook INT 60 and infect every .COM file run. After some time has passed, a "smiley" (ASCII 1) will appear on the screen and "eat" any zero it finds on the screen.

The virus seems not too well written - containing some unreachable code, but it is unusual in some ways.

If the virus is active in memory and you look at a directory containing infected files, the virus will make the directory entries appear as they were before the infection. That is, you will not see any increase in file length.