efforts and employs several of the above strategies. One famous example of an orchestrated attack is known as an oscillation attack. Denial of Service Attack. The attacker prevents the calculation and dissemination of reputation values in reputation systems by using Denial of Service method. Defense strategies Here are some strategies to prevent the above attacks. Preventing Multiple Identities Mitigating Generation of False Rumors Mitigating Spreading of False Rumors Preventing Short-Term Abuse of the System Mitigating Denial of Service Attacks See also Collaborative filtering Collective influence algorithm Commons-based peer production Defaulted executee Government by algorithm Honor system Influence-for-hire Karma Online participation Reputation capital Reputation management Sesame Credit Social Credit System Social currency Sharing economy Social reputation in fiction Social systems Social translucence Subjective logic Trust metric Web of trust Whuffie References D. Quercia, S. Hailes, L. Capra. Lightweight Distributed Trust Propagation. ICDM 2007. R. Guha, R. Kumar, P. Raghavan, A. Tomkins. Propagation of Trust and Distrust WWW2004. A. Cheng, E. Friedman. Sybilproof reputation mechanisms SIGCOMM workshop on Economics of peer-to-peer systems, 2005. Hamed Alhoori, Omar Alvarez, Richard Furuta, Miguel Muñiz, Eduardo Urbina: Supporting the Creation of Scholarly Bibliographies by Communities through Online Reputation Based Social Collaboration. ECDL 2009: 180-191 Sybil Attacks Against Mobile Users: Friends and Foes to the Rescue by Daniele Quercia and Stephen Hailes. IEEE INFOCOM 2010. J.R. Douceur. The Sybil Attack . IPTPS02 2002. External links Reputation Systems - 2008 tutorial by Yury Lifshits Contracts in Cyberspace - 2008 essay (book chapter) by David D. Friedman. Technology in society Social information processing Social influence Social networks Social systems