A method for detecting fraudulent sign-ups at a payment system is discussed. The method includes receiving a suspect sign-up request for creating a new user account at the payment system. The method includes providing access to a new duplicate user account responsive to receiving the suspect sign-up request, the new duplicate user account imitating the new user account. The method includes initiating a fraud determination of whether the suspect sign-up request is fraudulent. The method includes receiving a request from the user device, the request for adding a new financial account to the new user account. The method includes providing an indication of an addition of the new financial account to the new user account. The method also includes delaying the addition of the new financial account to the new user account until receiving results of the fraud determination.