|Disc containing Morris Code|
at Museum of Science
"Morris sought to program the Internet worm to spread widely without drawing attention to itself. The worm was supposed to occupy little computer operation time, and thus not interfere with normal use of the computers. Morris programmed the worm to make it difficult to detect and read, so that other programmers would not be able to "kill" the worm easily. Morris also wanted to ensure that the worm did not copy itself onto a computer that already had a copy. Multiple copies of the worm on a computer would make the worm easier to detect and would bog down the system and ultimately cause the computer to crash. Therefore, Morris designed the worm to "ask" each computer whether it already had a copy of the worm. If it responded "no," then the worm would copy onto the computer; if it responded "yes," the worm would not duplicate. However, Morris was concerned that other programmers could kill the worm by programming their own computers to falsely respond "yes" to the question. To circumvent this protection, Morris programmed the worm to duplicate itself every seventh time it received a "yes" response. As it turned out, Morris underestimated the number of times a computer would be asked the question, and his one-out-of-seven ratio resulted in far more copying than he had anticipated. The worm was also designed so that it would be killed when a computer was shut down, an event that typically occurs once every week or two. This would have prevented the worm from accumulating on one computer, had Morris correctly estimated the likely rate of reinfection.
"Morris identified four ways in which the worm could break into computers on the network: (1) through a "hole" or "bug" (an error) in SEND MAIL, a computer program that transfers and receives electronic mail on a computer; (2) through a bug in the "finger demon" program, a program that permits a person to obtain limited information about the users of another computer; (3) through the "trusted hosts" feature, which permits a user with certain privileges on one computer to have equivalent privileges on another computer without using a password; and (4) through a program of password guessing, whereby various combinations of letters are tried out in rapid sequence in the hope that one will be an authorized user's password, which is entered to permit whatever level of activity that user is authorized to perform.
"On November 2, 1988, Morris released the worm from a computer at the Massachusetts Institute of Technology. MIT was selected to disguise the fact that the worm came from Morris at Cornell. Morris soon discovered that the worm was replicating and reinfecting machines at a much faster rate than he had anticipated. Ultimately, many machines at locations around the country either crashed or became "catatonic." When Morris realized what was happening, he contacted a friend at Harvard to discuss a solution. Eventually, they sent an anonymous message from Harvard over the network, instructing programmers how to kill the worm and prevent reinfection. However, because the network route was clogged, this message did not get through until it was too late. Computers were affected at numerous installations, including leading universities, military sites, and medical research facilities. The estimated cost of dealing with the worm at each installation ranged from $200 to more than $53,000.
"Morris was found guilty, following a jury trial, of violating 18 U.S.C. Section 1030(a)(5)(A). He was sentenced to three years of probation, 400 hours of community service, a fine of $10,050, and the costs of his supervision."
- U.S. v. Morris, 928 F.2d 504 (2nd Cir. 1991)
The Morris Worm also resulted in the creation of multiple new federal projects such as CERT with the mission of researching, thwarting, and alerting the network to new possible threats.
Robert Morris is reportedly a professor at MIT.