The Robert Morris worm is widely acknowledged as the first computer worm to be distributed across the Internet and the first computer virus to receive mainstream media attention.

Designed by Cornell graduate student Robert Tappan Morris, Jr., the Morris worm was released Nov. 2, 1988, from the MIT campus to disguise its point of origin. The 99-line program was reportedly an experiment Morris created to measure the size of the ARPANET.

The program’s job was to record a statistic and search for other Internet-connected systems. However, a number of bugs and design flaws caused the program to target system vulnerabilities (namely the sendmail and finger implementations in Unix-based systems) and create more copies of itself than intended. This in turn caused buffer overflow and denial-of-service attacks on infected systems, rendering them useless within 90 minutes of initial infection.

In less than a day, the Morris worm affected approximately 10% of the 60,000 Internet-connected computers across the United States. Even if the infected systems were cleaned or rebooted, the worm would return and re-infect them. Each infection reportedly cost between $200 and $53,000 to remove and, according to the U.S. General Accounting Office, as much as $100 million may have been lost due to the Morris worm.

The Morris worm served as a wake-up call for the information security industry, drawing attention to the potential danger posed by computer viruses and the need for strong protections. It also resulted in the first conviction under the 1986 Computer Fraud and Abuse Act; Robert Morris was fined $10,000 and was sentenced to three years’ probation and 400 hours of community service.