A mobile device app may be provided with a communications registry describing network-based resources with which the app would like to communicate, including Internet Protocol (IP) addresses and Universal Resource Locators URLs of the network-based resources, for example. A local firewall on the mobile device allows the app to only communicate with the defined network-based resources in the communications registry. A user is presented with the communications registry prior to accepting download or installation. The user is thus alerted to which external resources are necessary to operate the app and which ones are not. Users would be warned when requested communication permissions are overly broad or relate to known threat locations. A threat score may be provided to users for self-mitigation.