1. A method comprising: applying a rule set to first data associated with first hosts and to second data associated with second hosts, and associating at least some of the second hosts with at least some of the first hosts, where: each of the first and second hosts is addressable on a computer network; the first hosts were discovered on a computer network at or prior to a first time; and the second hosts were discovered on a computer network at or prior to a second time, the second time being later than the first time; and identifying any second host that cannot be associated with a first host; where the rule set comprises multiple rules, each rule having a value, and at least two values are weighted differently.