The Morris worm or Internet worm was one of the first computer worms distributed via the Internet; it is considered the first worm and was certainly the first to gain significant mainstream media attention. It also resulted in the first conviction under the 1986 Computer Fraud and Abuse Act.^[1] It was written by a student at Cornell University, Robert Tappan Morris, and launched on November 2, 1988 from MIT. The worm was released from MIT to disguise the fact that the worm originally came from Cornell. (Incidentally, Morris is now an associate professor at MIT.)

Architecture of the worm

Disk containing the source code for the Morris Worm held at the Boston Museum of Science

The mistake

The critical error that transformed the worm from a potentially harmless intellectual exercise into a virulent denial of service attack was in the spreading mechanism. The worm could have determined whether or not to invade a new computer by asking if there was already a copy running. But just doing this would have made it trivially easy to kill; everyone could just run a process that would answer "yes" when asked if there was already a copy, and the worm would stay away. The defense against this was inspired by Michael Rabin's mantra, "Randomization." To compensate for this possibility, Morris directed the worm to copy itself even if the response is "yes", 1 out of 7 times ^[2]. This level of replication proved excessive and the worm spread rapidly, infecting some computers multiple times. Rabin remarked when he heard of the mistake, that he "should have tried it on a simulator first."

Effects of the worm

It is usually reported that around 6,000 major Unix machines were infected by the Morris worm. Paul Graham has claimed^[3] that

"I was there when this statistic was cooked up, and this was the recipe: someone guessed that there were about 60,000 computers attached to the Internet, and that the worm might have infected ten percent of them."

Gene Spafford created the Phage mailing list to coordinate a response to the emergency.

Robert Morris was tried and convicted of violating the 1986 Computer Fraud and Abuse Act. After appeals he was sentenced to three years probation, 400 hours of community service, and a fine of $10,000.^[4]

The Morris worm has sometimes been referred to as the "Great Worm", because of the devastating effect it had upon the Internet at that time, both in overall system downtime and in psychological impact on the perception of security and reliability of the Internet. The name derives from the "Great Worms" of Tolkien: Scatha and Glaurung.^[5]

See also

• Notable computer viruses and worms
• Buffer overflow

Notes and references

External links

• Cornell commission findings - in the ACM Digital Library ((from the abstract: "sheds new light and dispels some myths"))
• the full text of The Cornell commission findings (.pdf) is also available via paid subscription from the ACM Digital Library
• Archive of worm material, incl. papers and code
• An analysis of the worm by Eugene Spafford
• An analysis of the worm by Mark Eichin and Jon Rochlis
• "The Morris Internet Worm" by Charles Schmidt and Tom Darby
• RFC 1135 - "Helminthiasis of the Internet" - an analysis of the worm infestation
• "A Tour of the Worm", Don Seeley, Department of Computer Science, University of Utah (as posted by Francis Litterio)
• The Morris Worm
• A Report On The Internet Worm, by Bob Page, University of Lowell

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