A method of detecting network worms include the following steps: (1) Profiling the TCP connection information collected from the protected network, quantifying the plurality of statuses contained in the TCP connection information; (2) Clustering the connection profiles to discover all the anomaly clusters that are specified by the condition composing of several adaptive thresholds; (3) Correlating the anomaly clusters to result in a new cluster graph or to extend an existing cluster graph; (4) Issuing a security incident about the worm propagation according to the propagation condition that also composes of several adaptive thresholds; and (5) Keeping and maintaining the status of the cluster graphs.