Abstract: A method for detecting fraudulent activity on an online system might comprise acquiring data from online service providers about a plurality of interactions of users with the plurality of online service providers, building an identity profile of the user based on the data, receiving, from a client system, an API request, wherein the API request includes information about the user and a new user interaction apparently attempted by the user, comparing the information against the identity profile, and based on the comparing, generating an identity score for the new user interaction. If the identity score exceeds a threshold value, the method can comprise generating an alert, sending the alert to the user, receiving from the user an indication of whether the new user interaction was attempted by the user, and if the new user interaction was not attempted by the user, sending a report to the client system.