A device and a method for identifying whether a network node is infected by malware, including identifying indicator events for each of a plurality of anomaly indicators, by counting the number of occurrences of an anomaly indicator in at least one of a network node and an entire network during a predetermined time duration and if the number of occurrences of the anomaly indicator during the predetermined time duration is greater than a predetermined event threshold, identifying an indicator event associated with the anomaly indicator during the predetermined time duration and assigning an expiration duration for the indicator event, determining whether the identified indicator events fulfill at least one predetermined infection rule, and if the indicator events fulfill the at least one predetermined infection rule, identifying the network node as infected by malware.