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The Morris worm or Internet worm of November 2, 1988, was one of the first computer worms distributed via the Internet, and the first to gain significant mainstream media attention. It also resulted in the first felony conviction in the US under the 1986 Computer Fraud and Abuse Act.[1] It was written by a graduate student at Cornell University, Robert Tappan Morris, and launched on November 2, 1988, from the computer systems of the Massachusetts Institute of Technology.


Floppy Diskette containing the source code for the Morris Worm (Also known as The Worm) held at the Computer History Museum

According to its creator, Robert Tappan Morris, the Morris worm was not written to cause damage, but to highlight security flaws. The worm was released from MIT in the hope of suggesting that its creator studied there,[citation needed] which Morris did not (though Morris became a tenured professor at MIT in 2006).[2] It worked by exploiting known vulnerabilities in Unix sendmail, finger, and rsh/rexec, as well as weak passwords.[3] Due to reliance on rsh (normally disabled on untrusted networks), fixes to sendmail, finger, the widespread use of network filtering, and improved awareness of the dangers of weak passwords, it should not succeed on a contemporary, properly configured system.

A supposedly unintended consequence of the code, however, caused it to be more damaging: a computer could be infected multiple times and each additional process would slow the machine down, eventually to the point of being unusable. This would have the same effect as a fork bomb and crash the computer several times. The main body of the worm could only infect DEC VAX machines running 4BSD, and Sun-3 systems. A portable C "grappling hook" component of the worm was used to pull over (download) the main body parts, and the grappling hook could run on other systems, loading them down and making them peripheral victims.

The mistakeEdit

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 to invade a new computer by asking whether there was already a copy running. But just doing this would have made it trivially easy to stop, as administrators could just run a process that would answer "yes" when asked whether 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.[4] This level of replication proved excessive, and the worm spread rapidly, infecting some computers multiple times. Rabin said that Morris "should have tried it on a simulator first".[5]

Effects of the wormEdit

The U.S. Government Accountability Office put the cost of the damage at $100,000–10,000,000.[6] Clifford Stoll, who helped fight the worm, wrote in 1989, "I surveyed the network, and found that two thousand computers were infected within fifteen hours. These machines were dead in the water—useless until disinfected. And removing the virus often took two days."[7] It is usually reported that around 6,000 major UNIX machines were infected by the Morris worm; however, Morris's colleague Paul Graham claimed, "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."[8] Stoll wrote, "Rumors have it that [Morris] worked with a friend or two at Harvard's computing department (Harvard student Paul Graham sent him mail asking for 'Any news on the brilliant project')".[7]

The Internet was partitioned for several days, as regional networks disconnected from the NSFNet backbone and from each other to prevent recontamination, as they cleaned their own networks.

The Morris worm prompted DARPA to fund the establishment of the CERT/CC at Carnegie Mellon University, to give experts a central point for coordinating responses to network emergencies.[9] Gene Spafford also created the Phage mailing list to coordinate a response to the emergency.

Robert Morris was tried and convicted of violating United States Code: Title 18 (18 U.S.C. § 1030), the Computer Fraud and Abuse Act[10] in United States v. Morris. After appeals, he was sentenced to three years' probation, 400 hours of community service, and a fine of $10,050 plus the costs of his supervision.[11]

The Morris worm has sometimes been referred to as the "Great Worm", because of the devastating effect it had on 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 was derived from the "Great Worms" of Tolkien: Scatha and Glaurung.[12]


Robert Tappan Morris, the creator of the worm, was the son of Robert Morris, a cryptographer and "Father of the Internet" who, at the time, was working for the NSA.[13][14][15]

In popular cultureEdit

  • The 1995 film Hackers features a main character who releases a viral attack bearing several similarities to the Morris worm: the event takes place in 1988, infects over a thousand computers, causes a massive economic disruption, and results in its propagator being fined and put on probation.
  • In the visual novel Digital: A Love Story, the Morris worm is portrayed as a cover story for a large-scale attack on ARPANET and several bulletin board systems.
  • In the epilogue of his book The Cuckoo's Egg, Stoll details his efforts battling the Morris worm.
  • In Halt and Catch Fire, a virus that works in a similar way to the Morris worm is created to gauge the size of the network.
  • In Internet Explorer, a popular webcomic, a character based on the Morris worm was introduced[citation needed]

See alsoEdit

Notes and referencesEdit

  1. ^ Dressler, J. (2007). "United States v. Morris". Cases and Materials on Criminal Law. St. Paul, MN: Thomson/West. ISBN 978-0-314-17719-3.
  2. ^ "Robert Morris". csail. 2007. Archived from the original on August 3, 2008. Retrieved August 23, 2008.
  3. ^ "US vs. Morris". Retrieved 2014-02-05.
  4. ^ "Court Appeal of Morris". Retrieved 2014-02-05.
  5. ^ Maynor, David (2011). Metasploit Toolkit for Penetration Testing, Exploit Development, and Vulnerability Research. Elsevier. p. 218. ISBN 978-0-08-054925-5.
  6. ^ During the Morris appeal process, the U.S. Court of Appeals estimated the cost of removing the virus from each installation was in the range of $200–53,000. Possibly based on these numbers, Clifford Stoll of Harvard estimated the total economic impact was between $100,000–10,000,000.
  7. ^ a b Stoll, Clifford (1989). "Epilogue". The Cuckoo's Egg. Doubleday. ISBN 978-0-307-81942-0.
  8. ^ "The Submarine". Retrieved 2014-02-05.
  9. ^ "Security of the Internet. CERT/CC". 1998-09-01. Retrieved 2014-02-05.
  10. ^ United States v. Morris (1991), 928 F.2d 504, 505 (2d Cir. 1991).
  11. ^ "Computer Intruder is Put on Probation and Fined" by John Markoff, The New York Times. The total fine ran to $13,326, which included a $10,000 fine, $50 special assessment, and $3,276 cost of probation oversight.
  12. ^ "Great Worm".
  13. ^ "The Morris Worm Turns 30". Global Knowledge Blog. 2018-11-01. Retrieved 2019-01-29.
  14. ^ "Robert Morris (cryptographer)", Wikipedia, 2018-04-16, retrieved 2019-01-29
  15. ^ "Robert Tappan Morris", Wikipedia, 2019-01-04, retrieved 2019-01-29

External linksEdit