Methods, systems, and apparatus, including computer programs encoded on computer storage media, for network risk assessment. One of the methods includes obtaining information describing network traffic between a plurality of network devices within a network. A network topology of the network is determined based on the information describing network traffic, with the network topology including nodes connected by an edge to one or more other nodes, and with each node being associated with one or more network devices. Indications of user access rights of users are associated to respective nodes included in the network topology. User interface data associated with the network topology is generated.