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Lecture notes on Computer and network security: Lecture 22 - Avinash Kak

Lecture 22 - Malware: Viruses and worms. After studying this chapter you will be able to understand: Attributes of a virus, educational examples of a virus in Perl and Python, attributes of a worm, educational examples of a worm in Perl and Python, some well-known worms of the past, the conficker and stuxnet worms, how afraid should we be of viruses and worms? | Lecture 22: Malware: Viruses and Worms Lecture Notes on “Computer and Network Security” by Avi Kak (kak@purdue.edu) April 21, 2016 9:59am c 2016 Avinash Kak, Purdue University Goals: • Attributes of a virus • Educational examples of a virus in Perl and Python • Attributes of a worm • Educational examples of a worm in Perl and Python • Some well-known worms of the past • The Conficker and Stuxnet worms • How afraid should we be of viruses and worms? CONTENTS Section Title Page 22.1 Viruses 3 22.2 The Anatomy of a Virus with Working Examples in Perl and Python 6 22.3 Worms 12 22.4 Working Examples of a Worm in Perl and Python 15 22.5 Morris and Slammer Worms 32 22.6 The Conficker Worm 35 22.6.1 The Anatomy of Conficker.A and Conficker.B 44 22.6.2 The Anatomy of Conficker.C 49 22.7 The Stuxnet Worm 52 22.8 How Afraid Should We Be of Viruses and Worms 56 22.9 Homework Problems 62 2 Computer and Network Security by Avi Kak Lecture 22 22.1: VIRUSES • A computer virus is a malicious piece of executable code that propagates typically by attaching itself to a host document that will generally be an executable file. • Typical hosts for computer viruses are: – Executable files (such as the ‘.exe’ files in Windows machines) that may be sent around as email attachments – Boot sectors of disk partitions – Script files for system administration (such as the batch files in Windows machines, shell script files in Unix, etc.) – Documents that are allowed to contain macros (such as Microsoft Word documents, Excel spreadsheets, Access database files, etc.) 3 Computer and Network Security by Avi Kak Lecture 22 • Any operating system that allows third-party programs to run can support viruses. • Because of the way permissions work in Unix/Linux systems, it is more difficult for a virus to wreak havoc in such machines. Let’s say that a virus embedded itself into one of your script files. The virus code will execute only with the permissions that .