A virus is a quantity of genetic material (this could be RNA or DNA) usually encapsuled in a coat of protein called the capsid. It is an infectious agent that lives in other organisms. Virus can also refer to a computer virus, a type of damaging software (malware). In most games the virus is bad and must be stopped from spreading and destroyed. However, in other games you are the virus, and must save yourself by spreading as far as you can. Try playing a virus game here!