The present principles provide systems and methods for detecting robot-access of a web-based interface by utilizing a minimum expected human response time (MEHRT) to complete a pre-determined task. After a user is prompted to complete the pre-determined task, a user-response time is calculated. The user-response time is compared to the MEHRT and if the user-response time is less than the MEHRT, then the system determines that the user is a robot. Additionally and/or alternatively, the MEHRT may be employed to impose a time penalty on robots and thereby deter robot access of the interface. The time penalty may be imposed by preventing a user from completing the pre-determined task until the MEHRT has passed.