• A computer virus is a hidden, self-replicating program, usually containing malicious logic, that spreads by inserting copies of itself into and becoming part of another host program. It is designed to infect and take control of vulnerable systems without the user’s knowledge or consent, and is activated when the user launches or opens their main program. Computer viruses can cause frequent computer crashes or pop-up messages, damage or delete data on a computer, reformat a hard drive, use an email program to spread a virus to other computers, or flood a network with traffic, which ultimately makes it impossible to perform any activities on the Internet.