The tremendous success of the IoT is overshadowed by severe security risks introduced by IoT devices and smartphone apps to control them. Therefore, academia and industry increasingly acknowledge the use of in-network security approaches, such as IETF Manufacturer Usage Description (MUD), to restrict undesired communication. However, actual communication patterns of smart homes are not sufficiently covered by such policy-based approaches. In this paper, we propose to enforce MUD on authenticated smartphones to efficiently filter malicious traffic close to its origin and hinder further spreading. Such enforcement allows us to successfully mitigate the threat of malicious apps and IoT devices in smart home networks.