The gradual hybrid anti-worm (GHAW) was presented.It changed its confrontation scheme in real time according to the percentage of vulnerable hosts present in the network.For GHAW,its process of countering malicious internet worms was modeled.The performance of GHAW on two factors was also estimated:confronting validity against worms and consumption of network resources.Factors governing its performance,specifically the transformation threshold and the transformation rate,were analyzed.The simulation experiments show that GHAW has dynamical adaptability to changes of network conditions and offers the same level of effectiveness on confronting internet worms as the divide-and-rule hybrid anti-worm,with significantly less cost to network resources.The experiments also indicate that the transformation threshold is the key factor affecting the performance of GHAW.