A fraud prevention system is disclosed for preventing fraudulent activity on user accounts, the fraud prevention system interacting with a transaction tracking system for allowing association of transactions with user-defined categories. The fraud prevention system may include a computer memory including at least one database storing system settings specifying account-related events that require fraud prevention action and user-defined settings specifying account-related events that require fraud prevention action, wherein at least one of the user-defined settings pertains to events falling in one of the user-defined categories. The fraud prevention system may also include at least one computer processor programmed for detecting occurrence of the account-related events, accessing the system settings and user settings in the computer memory to determine if a fraud prevention action is required in response to the detected account-related event, activating a fraud prevention user interface for the user when fraud prevention action is required, and receiving user instructions through the fraud prevention interface and processing the user instructions.