With the wide application in modern industry and manufacturing, the security of cyber-physical systems has gradually become an important factor to ensure the healthy development of society, and has received extensive attention from scholars. Due to the deep integration of physical devices and communication networks within cyber-physical systems, the threat of network attacks on system security is becoming increasingly prominent. In this paper, we first summarize the characteristics of various network attacks from the attacker's perspective, and reveal the vulnerability of systems under different attacks. Secondly, in view of the characteristics of different network attacks, the secure state estimation, attack detection and secure control of cyber-physical systems are introduced from the defender's perspective, and the main application scenarios and advantages of each defense strategy are presented. Finally, the major challenges for the study of cyber-physical system security are proposed.