receiving, by a network management device, a uniform resource locator (URL) sent by an Internet of things terminal in an authentication process;

obtaining, by the network management device, a manufacturer usage descriptions (MUD) file based on the URL, and parsing the MUD file to obtain content of at least one field comprised in the MUD file, wherein the MUD file comprises a first-type field, the first-type field describes a security isolation requirement of the Internet of things terminal, and the first-type field comprises an isolated field indicating whether isolation is required among a plurality of Internet of things terminals including the Internet of things terminal; and

generating, by the network management device, a policy based on the content of the at least one field, wherein the content of the at least one field is obtained through parsing, and the policy controls a network service of the Internet of things terminal, to implement a requirement described in the content of the at least one field.