1. A fraud detection method implemented by a processor, the method comprising: receiving a fraud alert; investigating the fraud alert by analyzing social graph information and other available information of one or more users associated with the fraud alert to determine likelihood of the users being involved in fraud; when it is determined that a fraud was committed based on the analysis, reversing a chain of fraudulent transactions related to the fraud; and updating fraud events data related to the fraud into a fraud event database for subsequent analysis.