Morris is an example of:

Released on November 2, 1988, by Cornell University graduate student Robert Tappan Morris, the Morris Worm is a milestone in the history of cybersecurity.

Unlike a typical virus, which requires a host file or human action to spread, a computer worm is a standalone malware program that replicates itself in order to spread to other computers across a network.

The Mechanism: The Morris worm exploited known vulnerabilities in Unix sendmail, fingerd, and rsh/rexec utilities, alongside weak passwords.

The Impact: It was not designed to destroy data, but a coding error caused it to reinfect computers multiple times, heavily overloading systems and rendering thousands of computers unusable. This incident directly led to the creation of the first CERT (Computer Emergency Response Team) to handle internet-wide crises.