DNS wildcard beaconing. In one embodiment, for example, a computer-implemented method comprises: receiving a network request from a resolver to resolve a hostname, the network request from the resolver comprising a network address of the resolver, the hostname comprising a unique wildcard portion; storing first data representing an association between at least the unique wildcard portion and the network address of the resolver; receiving a network request from a client for a resource, the network request from the client comprising a network address of the client and at least the unique wildcard portion; storing second data representing an association between at least the unique wildcard portion and the network address of the client; based on the first data and the second data, associating the client with the resolver; and storing third data representing the association between the client and the resolver.