Viruses: Classification and Prevention

1. Viruses: Classification and Prevention Mike Morain

2. Basic Lecture Structure • History of malware • Nature and operation of malware • Discuss means of identification, removal, and prevention • Virtualization in malware

3. A Brief History • John Von Neumann • 1949 - Developed the first “self-replicating automata” • VeithRisak • 1972 - Wrote the first self-reproducing program for a SIEMENS 4004/35 computer • 1980 - JurgenKraus • Wrote a paper which put forward the idea that computer programs could act and behave like biological viruses • 1984 - Fred Cohen • Coined the term “virus” in his paper “Computer Viruses – Theory and Experiments”

4. Creeper • First controlled virus • Developed by Bob Thomas released on ARPANET in 1971for the TENEX OS • Behaved more like a modern worm • Would replicate itself onto machines around the NET, and display the message “I’m the creeper, catch me if you can!” • Would begin to print a file, pause, find a network system, and transfer • Relatively harmless. More a proof-of-concept than anything. Actually removed itself if it found another copy, then moved on.

5. The Elk Cloner • First virus to be released outside a single lab. First “uncontrolled” computer virus. (Skentra, ‘81) • Practical joke: spread via a floppy disk game, infected the host’s boot sector • The target OS: Apple DOS 3.3 • Relatively benign • Would print a poem on the target computer’s screen • From a recent NBC interview: • "I guess if you had to pick between being known for this and not being known for anything, I'd rather be known for this. But it's an odd placeholder for (all that) I've done."

6. Malware Today • Not so benign • Motivations: • Creating zombie machines for botnets (DDoS attacks, etc.) • Identity theft and impersonation • Monetary gains (credit card fraud, bank fraud, etc.) • Many other nefarious goals

7. Types of Viruses • Boot Sector • File • Macro • Encrypted • Stealth • Polymorphic • Metamorphic • Worms

8. A Structural Breakdown • Infection Mechanism • Trigger • Payload • Phases • Dormant Phase • Propagation Phase • Triggering Phase • Executing Phase

9. Example: MyDoom Worm • Infection Mechanism • E-mail attachment executable disguised as an image, document, etc. • Trigger • Opening the email attachment • Payload • 1. TCP Backdoor on port 3127 by overwriting local DLLs and running as a child process of Windows Explorer • 2. Launched a DDoS attack against the Caldera International (software company) on 1st of February, 2004

10. Infection Mechanism • The means by which a virus spreads • Early on, this was done via floppy drives, etc., but now Internet makes this far more easy. • Attach to common downloads, music, videos, software, screensavers etc. • Spread through emails as attachments • Spread on thumb drives (Pentagon example) • Infection vectors vary, payloads stay relatively constant • There are many other infection mechanisms: PDF files, infected image files, visiting infected web pages, office macros, etc.

11. Trigger • The mechanism by which the payload is activated. • For simply malicious viruses, this is often the simple act of opening the infected file • For more devious or surreptitious viruses, like trojanhorses, backdoors, or botnet infections, the trigger usually has to do with the intended purpose: • DDoS: Triggered by time/date to attack on, or by the controllers directly • Credit/Bank fraud: Activated when the user visits as bank site, etc. • The trigger is almost always related to the infection mechanism; the code needs to be executed somehow.

12. Payload • This is the intended action of the virus • Goals relatively constant • Malicious code (format hard drive, delete important files – old school) • Botnets • DDoS, hosting phishing sites, etc. • Trojans • back doors, keyloggers • Searching for personal of financial information

13. Ex: MS “Removal” Tool

14. MS Removal Tool (cont.) • Infection Mechanism • ActiveX Remote installation • ActiveX Data Objects tied to Wiindows APIs • Trigger • Begins execution on install • Payload • Hijacks various OS process calls • Changes web proxy

15. Combatting Malware • Prevention • Ideal solution • This requires detection during the propagation phase. • Detection, Identification, and Removal • Theoretically, much harder than prevention • The Malware may have spread already, so many files/machines will have to be checked and cleaned. • Removal requires knowing what it is, how it spread etc. • What do we do today?

16. Modern Antivirus Software • 1st Generation: simple scanners • Require signatures to detect the behavior of known viruses • Look at program length often and alert the administrators if anything has change • No so good for zero-day attacks

17. Tripwire http://original.jamesthornton.com/redhat/linux/9/Reference-Guide/figs/tripwire/tripwire.png

18. Modern Antivirus Software • 2nd Generation: heuristics scanners • Don’t really rely on the signatures as much, but use “rules of recognition” • They look for odd behavior, or code fragments that are often associated with viruses, but again, they don’t have specific signatures of every virus it can handle • Example of behavior: PyKeyLogger

19. Pykeylogger

20. Pykeylogger • Uses the SetWindowsHookEx API in Win32 • Specifically the WH_KEYBOARD and WH_KEYBOARD_LL • Commonly used APIs, but not in background. • Simple heuristic rule: • In general, don’t allow keyboard strokes to be captured in the background

21. Modern Antivirus Software (cont.) • 3rdGeneration: activity traps • More like the anomaly detection scheme, where this program just combs memory and looks for actions that are a threat to security rather than structures in the program code in memory • This has the distinct advantage of being able to prevent actions proactively rather than be responding retroactively. • 4th Generation: full-featured scanners • All of these tools combined and used simultaneously

22. Modern Antivirus Software (cont.) • The differences: • Older software scanned once a day, etc. Now they are working constantly to prevent infection • Norton, McAfee: all had original versions that did scheduled scans or on-boot scans based on signatures • Progress adds features as malware authors find exploits • Commercial Examples • Norton 2006 (13.0) introduced Internet Explorer and host file protection • Panda Antivirus is award winning • Detects all strange behavior, very good anomaly detection • Balance between good and annoying

23. Case Study: Microsoft Security Essentials • Microsoft has never really been known for security prowess • They’ve had some of the most embarrassing mishaps when it comes to security: • A few years ago, they released a “Malicious Software Removal Tool.” • It actually got pretty good reviews, and the methodology used was good • Unfortunately for MS, it worked so well it removed Internet Explorer as a potential security threat.

24. MSE Example (cont.) • Today’s solution: Microsoft Security Essentials, and is being lauded as a very well developed antivirus tool. • It uses a combination of signature and anomaly detection to fight infection. • Advances in hardware and speed allow constant protection to be done without extremely noticeable overhead.

25. MSE Example (cont.) • It has (as do many other tools): • Integration with the computer’s API calls • For instance, when you open a folder with an infected file, MSE does quick analysis on those files, and will alert you if it’s obviously infected, and does so without consuming too many resources • Also has the ability to scan every file for every known signature of virus. • Sandboxes programs that are behaving suspiciously and alerts the user

26. Further Advances in AV • The advancement of viruses and antiviruses is inseparably linked. • Once the current threats are dealt with, it’s hard to predict what virus makers will do next, so it’s a tango back and forth. • A huge flaw in even 4th Generation anti-virus software is the inability to track and detect polymorphic viruses

27. Digital Immune Systems

28. Digital Immune Systems • 1. A monitoring program on each PC uses anomaly detection to analyze behavior, and sends the suspicious activity to the admin machine. • 2. The admin machine encrypts the sample and sends it to a “central virus analysis (CVA).” • 3. The CVA creates a VM for running the infected program, analyzes the behavior, and produces a fix which is sent out to clients. • 4. Subscribers world-wide receive the new signatures and patches.

29. Digital Immune Systems

30. Digital Immune Systems • 1. A monitoring program on each PC uses anomaly detection to analyze behavior, and sends the suspicious activity to the admin machine. • 2. The admin machine encrypts the sample and sends it to a “central virus analysis.” • 3. The CVA creates a VM for running the infected program, analyzes the behavior, and produces a fix which is sent out to clients. • 4. Subscribers world-wide receive the new signatures and patches.

31. Digital Immune Systems

32. Digital Immune Systems • 1. A monitoring program on each PC uses anomaly detection to analyze behavior, and sends the suspicious activity to the admin machine. • 2. The admin machine encrypts the sample and sends it to a “central virus analysis.” • 3. The CVA creates a VM for running the infected program, analyzes the behavior, and produces a fix which is sent out to clients. • 4. Subscribers world-wide receive the new signatures and patches.

33. Digital Immune Systems

34. Digital Immune Systems • 1. A monitoring program on each PC uses anomaly detection to analyze behavior, and sends the suspicious activity to the admin machine. • 2. The admin machine encrypts the sample and sends it to a “central virus analysis.” • 3. The CVA creates a VM for running the infected program, analyzes the behavior, and produces a fix which is sent out to clients. • 4. Subscribers world-wide receive the new signatures and patches.

35. Digital Immune Systems

36. Generic Decryption • Solves this problem by running code through a fast “generic decryption” scanner that: • Has a CPU emulator that the suspicious code is allowed to be executed on. • The system looks for any commonly known encryption/decryption behavior, since this is often how polymorphic viruses change themselves. • Also includes the signature scanner from other generations. • Halts the code if it’s determined to be malicious, and “quarantines” the original executable. • Works a lot like TaintCheck • The problem with this is that it requires a lot of overhead.

37. Virtualization in Anti-virus • Hardware advances – mainly speed of processors, multiple cores, and more memory – allow virtualization to be used • Example: Sunbelt Software’s Vipre Enterprise Malware Client • Maintains a minimized, mimicked copy of the host system in a sandbox of memory and allows suspect files to run free. • Implementation utilizing the advancement of processor virtualization and multi-core assignment minimizes the overhead. • The virtualization, along-side a proprietary “dynamic translation” re-compiler is how this works so quickly and well

38. Sunbelt Vipre

39. Sunbelt Vipre

40. Sunbelt Vipre http://www.sunbeltsoftware.com/developer/VIPRE-Desktop-SDK/

41. Conclusions • Digital immune systems are the way of the future • Virtualization allows them to be implemented locally on a small scale • Still benefit from honeypots that security companies run to catch all the viruses going around. • OS integration is key