Viral Rewind: Virus.DOS.Walker

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. Looking at the very simple and straightforward Walker virus for DOS. It's a memory-resident file-infector like most viruses you'd expect. It infects .EXEs and .COMs and because it isn't stealthy the file size will increase. However, Walker is mainly known for it's graphical payload...

The payload: When an infected file is run, Walker's payload activates instantly (no prerequisites are required). First, it plays a little audio bit over the PC internal speaker. It then plays it again followed by a graphic of what the virus author dubs "Sara's Groove" (and is blurred here for obvious reasons). With Walker now loaded into memory, every ten seconds or so an animated figure walks across the screen (hence the virus name). The figure is derived from the game "Bad Street Brawler" (it's an enemy) and everytime the figure appears DOS stops responding until the animation finishes.

And if a file that is used during startup is infected, Walker will launch the "walking man" payload upon execution.

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[williamdrum]

I'm kind of curious how they did this and made it run constantly in the background