Resource-constrained mobile devices pose a challenge to the design of security mechanisms. Existing host-based malware detection solutions are often resource-intensive. The authors present a decentralized and resource-aware malware detection architecture for mobile devices. Their approach leverages two key ideas: social collaboration and the concept of a hot set. The hot set concept states that not all malware signatures are equally important. At any given time, some signatures (the hot set) are more likely to be matched than the others.