Apart from these “personal strikes,” there are also “signature strikes,” here meaning strikes authorized on the basis of traces, indications, or defining characteristics. Such strikes target individuals whose identity remains unknown but whose behavior suggests, signals, or signs membership in a “terrorist organization.” … In such cases, the strike is made “without knowing the precise identity of the individuals targeted.” It depends solely on their behavior, which, seen from the sky, appears to “correspond to a ‘signature’ of pre-identified behavior that the United States links to militant activity.” Today, strikes of this type, against unknown suspects, appear to constitute the majority of cases.

Grégoire Chamayou, A Theory of the Drone, loc. 211