For a computer virus to spread through a computer system, or network, it must be activated. This means that the file that contains the virus must be opened, or executed in order for the virus to come to life. After it gets activated, these viruses look for certain programs to infect. The main and the important that you must note is that, all viruses seem to do well is duplicate themselves within the programs they find, and this is the main reason as to how they spread well.
There are a lot of effects that a virus can cause on your computer depends on how it has been programmed to spread. These / this programming can be one of two types: One is the resident and the other is the non-resident. The non-resident viruses are made up of two processes -one finds files on your computer to infect, and the other duplicates the virus.
Resident viruses are made up of only one process. The sole function is to duplicate itself throughout your computer. To perform this action, resident viruses are programmed to load into the computer's memory and the virus itself is activated every time you turn your computer on. This process continues as long as the system is on.
Thanks to L&C Sunshine Technology Services.