In one embodiment, a method includes obtaining a set of samples, each of the set of samples including sample values for each of a plurality of variables in a variable space. The method includes receiving, for each of an initial subset of the set of samples, a label for the sample as being either malicious or legitimate; identifying one or more boundaries in the variable space based on the labels and sample values for each of the initial subset; selecting an incremental subset of the unlabeled samples of the set of samples, wherein the incremental subset includes at least one unlabeled sample including sample values further from any of the one or more boundaries than an unlabeled sample that is not included in the incremental subset; and receiving, for each of the incremental subset, a label for the sample as being either malicious or legitimate.