1. “It is better to suffer wrong than to do it, and happier to be sometimes cheated than not to trust..” Samuel Johnson Trust and reputation Systems, Attacks and Problems Steve Marsh Carleton University, November 30th, 2009 steve.marsh@crc.gc.ca © stephen marsh, 2009

2. Outline Defences Caveats Pondering… Attacks on Trust and Reputation

3. Whitewashing

4. Reputation play (conmen) Reputation lag

5. Sockpuppets Meatpuppets

6. Sybil

7. Collusion

8. Reputation Theft & Impersonation

9. Denial-of-reputation

10. Ballot Stuffing

11. Bad Mouthing

12. Extortion

13. Repudiation of data Repudiation of transaction

14. Recommender dishonesty

15. Privacy

16. Discrimination

17. The Herd

18. The Vocal Minority

19. Underlying network threats

20. Trust Threats

21. linkbombs, linkspam, spamdexing

22. Bootstrap issues

23. Expectations

24. Thinking about defence and improvement

25. Accountability

26. Tempus fugit

27. Speed is of the essence

28. Making Sybil expensive

29. Prove it…

30. Acknowledgements

31. Escrow

32. Local and Global Calculations

33. The Sound of Silence

34. I need a receipt

35. How heavy are you?

36. Controlled Anonymity

37. Talk about it

38. CAPTCHA

39. You are responsible

40. Caveats

41. Ponder this

42. Where next?

43. Resources