In some implementations, a method includes receiving, for each of multiple users, user activity data describing actions taken by the user by use of a user device over a period of time, determining, for each user and based on the actions taken by the user over the period of time and user responsibility data that describe responsibilities of the user, a risk assessment representative of a security risk resulting from the actions taken by the user by use of the user device, and determining, by the data processing apparatus, for each user and based on the risk assessment determined for the user, whether to implement a user-specific remedial action directed to risk mitigation.