Program (script) capable of harming the system in which it was launched.

By harm are meant:

  • errors in work;
  • blocking user access;
  • deletion or damage to files;
  • data encryption;
  • interception of important information (for example, payment data), etc.

Typically, viruses have the ability to self-disseminate by cloning, infecting certain types of files, invading from internet through sites etc.