1. A fraud detection method implemented by a processor, the method comprising: receiving a fraud alert, the fraud alert initiated by a user and detected by a system executing the method; investigating the fraud alert by analyzing social graph of the user associated with the fraud alert to determine likelihood of the user being involved in fraud; when it is determined that the user was involved in the fraud based on the analysis, reversing a chain of fraudulent transactions related to the fraud; updating fraud events data related to the fraud into a fraud event database for subsequent analysis, wherein analyzing further includes examining information obtained from the social graph of the user associated with the fraud alert to determine if the user submitted a false claim, the examining includes, determining different types of links between the user associated with the fraud alert and other users in the social graph, each type of link accorded a distinct weight; and examining the weights associated with each of the different types of links to determine level of linkage of the user with the other users in the social graph, the type of links and level of linkage between the user and the other users in the social graph used in determining if a false claim was submitted by the user through the fraud alert, wherein the method operations are performed by the processor.