Our last post covered some of the ways that Rumble gathers information from DNS services. While working on the tracer implementation, we identified a trick that other folks might find it useful. It turns out that most DNS resolvers do not filter the address ranges they will contact when handling a request, allowing for remote subnet “ping scans” with a little work. This technique isn’t foolproof, and is probably not new, but it may have interesting security implications.

DNS is an amazing protocol. After starting life as a simple mechanism for name resolution, it is now used to enforce TLS rules, prevent email impersonation, authorize users, protect endpoints, enable service discovery, and much more. DNS services run across a range of devices and provide quite a bit of information about the environment, given the right queries. This post describes the techniques used by the Beta 2 version of Rumble Network Discovery to identify DNS services.