Explain how a computer virus works.
A computer virus exists in an infected program. When a user runs an infected program, the computer copies the program into RAM. The viral code runs before the user-initiated program. The virus copies itself to another part of RAM so that it can continue to run after the user starts running other software. Then the virus passes control back to the infected program. When the user runs a different program the virus begins running again, then inserts itself into that software.