The trend toward energy-proportional computing, in which power consumption scales closely with workload, is making computers increasingly vulnerable to information leakage via whole-system power analysis. Saving energy is an unqualified boon for computer operators, but this trend has produced an unintentional side effect: it is becoming easier to identify computing activities in power traces because idle-power reduction has lowered the effective noise floor. This paper offers preliminary evidence that the analysis of AC power traces can be both harmful to privacy and beneficial for malware detection, the latter of which may benefit embedded (eg, medical) devices.