Abstract: Artificial Immune Systems (AIS) including the Dendritic Cell Algorithm (DCA) are an emerging method to detect malware in computer systems. A DCA module may receive an output or signal from multiple indicators concerning the state of at least a portion of the system. The DCA module is configured to combine the plurality of signals into a single signal vector. The DCA module may be configured to sort the received signals based on signal type and magnitude of each signal. The DCA module may then use a decay factor to weight the received signals so that a large number of “nominal” signals do not drown out a small number of “strong” signals indicating a malware attack. The decay factor may be exponentially increased each time it is applied so that all received signals are considered by the DCA module, but so that the “nominal” signals may have a minimal effect.