Sleeper agents; magical time-bombs set to hunt down Death Eaters with no formal training to reduce civilian casualties.  No wonder Kingsley wasn't willing to make just anyone an Auror... you'd have to trust them to not abuse the power.  Harry remembered what Hermione had said. Draco would more than likely be a target, but so might be Narcissa.  What's the difference between a Death Eater, a scared boy forced to take the mark, and the wife of a Death Eater to an Auror?