Internet worm is harmful to network security,and it has become a research hotspot in recent years.A thorough survey on the propagation models and defense techniques of Internet worm is made in this paper.We first give its strict definition and discuss the working mechanism.We then analyze and compare some repre-sentative worm propagation models proposed in recent years,such as K-M model,two-factor model,worm-anti-worm model(WAW),firewall-based model,quarantine-based model and hybrid benign worm-based model,etc.Some typical defense techniques such as virtual honeypot,active worm prevention and agent-oriented worm defense,etc.,are also discussed.The future direction of the worm defense system is pointed out. Internet worm is harmful to network security, and it has become a research hotspot in recent years. A thorough survey on the propagation models and defense techniques of Internet worm is made in this paper. We first give its strict definition and discuss the working mechanism. We then analyze and compare some repre-sentative worm propagation models proposed in recent years, such as KM model, two-factor model, worm-anti-worm model (WAW), firewall-based model, quarantine-based model and hybrid benign worm -based model, etc.Some typical defense techniques such as virtual honeypot, active worm prevention and agent-oriented worm defense, etc., are also discussed. future of the worm defense system is pointed out.