A computer virus is a type of malware that spreads by inserting a copy of itself into another program and becoming part of it. It spreads from one computer to another, leaving infections in transit.
Viruses can range in severity from mildly annoying to data or software corruption and denial of service (DoS) conditions.
Almost all viruses are attached to an executable file, which means that a virus can exist on the system, but will not be active and cannot spread until the user launches or opens a malicious host file or program.
When the host code is executed, the virus code is also executed. Usually, the main program continues to run after being infected with a virus.
However, some viruses overwrite other programs with their copies, which completely destroys the main program.
Viruses spread when the software or document to which they are attached is transferred from one computer to another using a network, disk, file sharing, or infected email attachments.
- The main purpose of a virus is to change information.
- The virus cannot be controlled remotely.