A facility for interacting with data networks using a permanent network identifier persistently stored within a computing system is described. In one example facility, in response to each opportunity to connect to a data network, the facility identifies information for the data network, and determines whether the determined identifying matches any of a set of approved data networks. In response to determining that it does, the facility establishes a connection with the first data network using the computing system's permanent network identifier, and conducts the established connection with the first data network using the computing system's permanent network identifier. In response to determining that it does not, the facility establishes a connection with the data network using a temporary network identifier that is different from the computing system's permanent network identifier, and conducts the established connection with the data network using the temporary network identifier.