computer science

Parasitic viruses, also known as fi le viruses, spread by attaching
themselves to programs.

When you start a program infected with a parasitic virus, the virus code is run. To hide
itself, the virus then passes control back to the original program.
The operating system on your computer sees the virus as part of the program you were
trying to run and gives it the same rights. These rights allow the virus to copy itself,
install itself in memory or make changes on your computer.
Parasitic viruses appeared early in virus history but they can still pose a threat.