Once it is running, it is then able to infect other programs or documents. Biological virus is a fragment of DNA inside protective jacket. Instead, virus must inject its DNA into a cell. The viral DNA then uses the cell s existing machinery to reproduce itself. How viruses work.
Any virus is designed so it runs first when the legitimate program gets executed.
The virus loads itself into memory and looks around to see if it can find any other programs on the disk. If it can find one it modifies it to add the virus s code to unsuspecting program. Then the virus launches the real program . The user really has no way to know that the virus ever runs. Unfortunately, the virus has now reproduced itself so two programs are infected.