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With Microscope and Tweezers:

An Analysis of the Internet Virus of November 1988 ?

Mark W. Eichin and Jon A. Rochlis

Massachusetts Institute of Technology

77 Massachusetts Avenue, E40-311

Cambridge, MA 02139

February 9, 1989


In early November 1988 the Internet, a collection of networks consisting of 60,000 host computers implementing the TCP/IP protocol suite, was attacked by a virus, a programwhich broke into computers on the network and which spread from one machine to another. This paper is a detailed analysis of the virus programitself, as well as the reactions of the besieged Internet community. We discuss the structure of the actual program, as well as the strategies the virus used to reproduce itself. We present the chronology of events as seen by our team at MIT, one of a handful of groups around the country working to take apart the virus, in an attempt to discover its secrets and to learn the network's vulnerabilities. We describe the lessons that this incident has taught the Internet community and topics for future consideration and resolution. A detailed routine by routine description of the virus program including the contents of its built in dictionary is provided.

1 Introduction

The Internet[1][2], a collection of interconnected networks linking approximately 60,000 computers, was attacked by a virus program on 2 November 1988. The Internet community is comprised of academic, corporate, and goverment research users, all seeking to exchange information to enhance their research efforts.

The virus broke into Berkeley Standard Distribution (BSD) UNIX1 and derivative systems. Once resident in a

?Copyright c 1988 Massachusetts Institute of Technology. A version of this paper will be presented at the 1989 IEEE Symposium on Research in Security and Privacy.
1UNIX is a trademark of AT&T. DEC, VAX, and Ultrix are trademarks of Digitial Equipment Corporation. Sun, SunOS, and NFS are trademarks of Sun Microsystems, Inc. IBM is a trademark of International Business Machines, Inc.

computer, it attempted to break into other machines on the network. This paper is an analysis of that virus program and of the reaction of the Internet community to the attack.

1.1 Organization

In Section 1 we discuss the categorization of the program which attacked the Internet, the goals of the teams working on isolating the virus and the methods they employed, and summarize what the virus did and did not actually do. In Section 2 we discuss in more detail the strategies it employed, the specific attacks it used, and the effective and ineffective defenses proposed by the community. Section 3 is a detailed presentation of the chronology of the virus. It describes how our group at MIT found out and reacted to the crisis, and relate the experiences and actions of select other groups throughout the country, especially as they interacted with our group. Once the crisis had passed, the Internet community had time not only to explore the vulnerabilities which had allowed the attack to succeed, but also to consider how future attacks could be prevented. Section 4 presents our views on the lessons learned and problems to be faced in the future. In Section 5 we acknowledge the people on our team and the people at other sites who aided us in the effort to understand the virus.

We present a subroutine by subroutine description of the virus program itself in Appendix A, including a diagram of the information flow through the routines which comprise the ``cracking engine''. Appendix B contains a list of the words included in the built-in dictionary carried by the virus. Finally in Appendix C we provide an alphabetized list of all the people mentioned in this paper, their affiliations, and their network mail addresses.