How do you design a good computer virus?

Answer 1

By definition, a computer virus must transmit and be self-replicating. There is no requirement for a payload. So the way to do this is to either find an existing flaw or exploit in the front end of an operating system and allows you to insert code instead of date, and then have the target machine execute the code, or to use a form of social engineering to insert the code into the user's machine, or simply insert the code as you would any other executable process. Note that not all viruses are bad. The purpose and the payload are not part of the definition.