COMPUTER VIRUSES

1. COMPUTER VIRUSES Christopher Motl February 21, 2008

2. Computers & Viruses History of Computer Viruses How Viruses Work Virus Detection\Removal\Analysis Alternative Detection Method Computer Immune System Miscellaneous Other Topics OVERVIEW

3. COMPUTERS AND VIRUSES

4. What is a Computer? COMPUTERS AND VIRUSES • “A computer is a machine that manipulates data according to a list of instructions.” • “A computer is, at its most basic, a machine which can take instructions, and perform computations based on those instructions.” • “Computers are not very intelligent devices, but they handle instructions flawlessly and fast.” • “A computer is an electronic device that executes the instructions in a program.”

5. What is a Virus? COMPUTERS AND VIRUSES • “A virus is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell.” • “A virus is not strictly alive.. nor is it strictly dead... A virus has some fundamental information which allows it to make copies of itself. However, the virus must be inside a living cell of some kind before the information can be used.” • “Viruses are not living cells, but efficient parasites that commandeer living cells and turn them into virus factories.” • “an ultramicroscopic, metabolically inert, infectious agent that replicates only within the cells of living hosts, mainly bacteria, plants, and animals: composed of an RNA or DNA core, a protein coat, and, in more complex types, a surrounding envelope.”

6. What is a Computer Virus? COMPUTERS AND VIRUSES • “Computer Viruses are self replicating software entities that attach themselves parasitically to existing programs.” • “We define a computer 'virus' as a program that can 'infect' other programs by modifying them to include a possibly evolved copy of itself.” • “A computer virus is a self-replicating computer program that spreads by attaching itself to executable files or system areas on diskettes.” • “Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.”

7. HISTORY OF COMPUTER VIRUSES

8. The Beginnings HISTORY OF COMPUTER VIRUSES • Early 1980’s - University of Southern California • Leonard Adleman • Computer Science & Molecular Biology • Famous for work with Rivest and Shamir on RSA • DNA Computing • Coined the term “Computer Virus” • Fred Cohen • PhD student under Adleman • Created the first ‘real’ computer virus November 10, 1983 • Parasitic application that seized control of computer operation

9. Statistics HISTORY OF COMPUTER VIRUSES

10. HOW VIRUSES WORK

11. Virus Life Cycle HOW VIRUSES WORK • Attachment • Penetration • Uncoating • Replication • Assembly • Release

12. Computer Virus Life Cycle HOW VIRUSES WORK

13. Infection of a Program HOW VIRUSES WORK

14. VIRUS DETECTION\REMOVAL\ANALYSIS

15. Virus Detection VIRUS DETECTION\REMOVAL\ANALYSIS • The goal of anti-virus software is to detect all viral infections on a given computer system and to restore each infected program to its original uninfected state. If possible. • Activity Monitors • Alert user to system activity that is indicative of a virus. • Integrity Management Systems • Warn user of suspicious changes to files. • These methods can detect presence of unknown viruses, but they are not often able to pinpoint the nature or even location of the infecting agent. Normal, legitimate activity can also be flagged, causing a nuisance and disrupting normal work. This can lead to the warnings being completely ignored.

16. Virus Detection & Removal VIRUS DETECTION\REMOVAL\ANALYSIS • Virus Scanners scour the file system, searching through files, boot records, memory, and anywhere else executable code can be stored, searching for characteristic byte patterns (Signatures) that are identifying portions of viruses. • Scanners provide much more specific detection than activity monitors and integrity management systems, and are essential for establishing the identity and location of a virus. • Disinfectors use the identity and location information to restore programs to their original states. • Scanning and repairing can only be applied to known viruses and variants • Every Virus strain must be examined individually to extract signatures and information on how to remove it.

17. Virus Analysis VIRUS DETECTION\REMOVAL\ANALYSIS • Once a new virus is discovered, it is passed around a group of anti-virus experts. • A human expert disassembles the virus and then analyzes the code to determine both behavior and the method it uses to attach itself to host programs. • The expert than extracts a signature that is guaranteed to be found in each instance of the virus, but which is unlikely to be found in normal programs. • The new signature is added to the database so that this virus can be detected and removed in the wild. • This is a very time consuming process, taking anywhere from hours to days to complete, and it is possible that a bad signature can be chosen.

18. ALTERNATIVE DETECTION METHOD

19. Generic Detection of Viruses ALTERNATIVE DETECTION METHOD • In the middle of Scanners and Activity Monitors/Integrity Management Systems, lies the generic detector. • A Generic Detector takes a programs code as input and determines whether or not the program is viral or non-viral. • Perfect Generic Detection is an NP-Complete problem, which is reducible to the Halting Problem • Imperfect Generic Detection, however, is possible, and turns out to be a problem in pattern classification.

20. Imperfect Generic Detection ALTERNATIVE DETECTION METHOD • The basic concept of machine learning is applied to virus detection. • Very similar to concepts in Robot Vision for face/object detection. • Features are selected, and then classifiers are trained. • 85% detection rate. Other 15% escape detection due to code obscuring techniques. • This method works well for boot sector viruses, but has a few drawbacks • New viruses can be detected only if they have a sufficient amount of code in common with known viruses. • The method is appropriate for viral detection only, and is incapable of aiding in removal of a virus from an infected boot sector or file.

21. COMPUTER IMMUNE SYSTEM

22. Motivation COMPUTER IMMUNE SYSTEM • The Generic Detection system is a good start, but is a static, non-adaptive system. • An adaptive system, such as out own immune system is much better. • The immune system responds to virus-like anomalies by capturing and analyzing viral samples. • The samples are analyzed, and a means for detecting and removing the virus are found.

23. Biological Defense COMPUTER IMMUNE SYSTEM • Anomaly Detection • The ability to determine self from non-self, the existence of things which are not a part of the system. • Scanning for Known Viruses • Parallel searching through all known virus signatures looking for a match. • Virus Removal • A known virus has been discovered and is now removed. • Decoys • An anomaly has been detected that does not match any known virus signature. • Decoys, or programs which are very attractive to viruses, are placed out to bait the viruses.

24. Biological Defense COMPUTER IMMUNE SYSTEM • Automatic Virus Analysis • Once several decoys have become infected with the virus, they can be compared and the inner workings of the virus can be discovered. • Automatic Signature Extraction • A signature that will minimize false negatives and false positives is the goal of this phase. • It should be likely to be found in all instances of the virus, but not in normal programs. • Immunological Memory • Add analysis data and signature of new virus to known virus database for quick lookup later.

25. Immune System Overview COMPUTER IMMUNE SYSTEM

26. MISCELLANEOUS OTHER TOPICS

27. Worms & Trojan Horses & Other Non-viruses MISCELLANEOUS OTHER TOPICS • Worm • A worm can spread itself to other computers without needing to be transferred as part of a host • Trojan Horse • A Trojan horse is a file that appears harmless until executed. • A program that does not replicate is not a virus, regardless of whether it is malicious or not. Maliciousness in a program does not make it a virus.

28. Can your cat get a Computer Virus? MISCELLANEOUS OTHER TOPICS

29. RFID Viruses MISCELLANEOUS OTHER TOPICS • RFID – Radio Frequency Identification • RFID Virus uses RFID to spreads primarily by means of SQL Injection. • Everything about regular viruses still apply to RFID Viruses. • The primary attack of RFID Viruses is focused on Databases.

30. RFID Viruses MISCELLANEOUS OTHER TOPICS • Examples • Supermarket uses RFID to scan merchandise. • Veterinarian uses RFID embedded in pets to find information about animals. • Airport baggage handling system uses RFID to route baggage.

31. RFID Viruses MISCELLANEOUS OTHER TOPICS

32. RFID Viruses MISCELLANEOUS OTHER TOPICS

33. QUESTIONS

34. Homework • What feature is a requirement for a program to be a virus? • If a program is self-replicating, but does nothing malicious, is it still a virus?