In theory, a cyber attack on traffic signal equipment is possible, which may lead to traffic chaos. Modern traffic signal systems are usually connected to the network and have the following risks： 1. If the traffic signal system lacks sufficient network security protection, an attacker may invade the system. 2. A successful attack may cause the signal light to malfunction, display incorrect instructions, or turn off completely. 3. This may indeed cause traffic chaos and even cause safety risks However, most cities have implemented multi-layer security measures to protect these critical infrastructures.： -Network isolation and firewall -Encrypted communication -Anomaly detection system -Fail-safe mechanism (automatically switch to a safe state when the system detects an abnormality) This is an important issue that continues to be of concern in the field of network security and infrastructure protection, and cities are constantly strengthening the security of these systems.