Virus Droppers

Normally, you obtain a virus by either attempting to boot from an infected floppy disk, by running an infected file, or by loading an infected document with viral macro commands in it. There is another way you can pick up a virus: by encountering a virus dropper. These are rare, but now and again someone will attempt to be clever and try to program one.

Basically, a dropper is just what the name implies: a program designed to run and install (or "drop") a virus onto your system. The program itself is not infected nor is it a virus because it does not replicate. So, technically, a dropper should be considered a Trojan. Often, because the virus is hidden in the program code, a scanner will not detect the danger until after the virus is dropped onto your system. (It's technically possible to write a virus that also drops other viruses, and several have been tried. Most are very buggy, however.)

It's a technical point, but there is a class of dropper that only infects the computer's memory, not the disk. These are given the name injector by some virus researchers.

Summary

• A Trojan program that installs a virus onto your system is called a dropper.
• Fortunately, because of technical difficulties, droppers are hard to program and therefore rare.

That's the end of the introduction. Now for the detail...