Manufacturer Usage Description (MUD) is a network control model for IoT and other managed devices. A manufacturer publishes a policy that describes the device’s expected traffic: what destinations it should contact, which protocols it uses, and what it should never do. Security tools then enforce that allow-list on the network.
MUD matters because many compromised devices become dangerous mainly when they can call out freely to command-and-control servers, scan internal networks, or join botnets. By limiting outbound and inbound communication to known patterns, MUD reduces the blast radius of a compromise and makes unusual behavior easier to spot. In practice, it is used in enterprise and home networks to keep smart devices on a narrow leash: a camera can reach its update service, but not arbitrary internet hosts. It is a defense-in-depth control, not a replacement for patching, strong passwords, or segmentation.