Abstract: Embodiments of this application disclose a manufacturer usage description (MUD) file obtaining method and a device. A MUD controller uses a verified valid MUD uniform resource locator (URL) as a trusted basis. When a terminal device is currently updated, the MUD controller obtains a new MUD file based on a new MUD URL that meets a matching condition with the trusted MUD URL. Alternatively, the MUD controller uses fixed attribute information of a valid MUD URL as a trusted basis. When a terminal device is currently updated, the MUD controller obtains an updated MUD URL based on the trusted fixed attribute information and newly received variable attribute information, and obtains a new MUD file.