TCP/102 is a network port commonly used by Siemens S7 communication in industrial control systems. In OT environments, it often carries traffic between engineering workstations, PLCs, and maintenance tools that read, write, or monitor controller data. Because it sits close to the control plane, exposure on this port can matter more than a typical IT service port.
Security teams care about TCP/102 because unauthorized access to S7 services can allow attackers to inspect processes, change logic, or interfere with availability. In real attacks, defenders may see scans, connection attempts, or suspicious commands targeting this port from flat networks or weak remote-access paths. In defense, TCP/102 is usually inventoried, restricted to trusted hosts, segmented away from business networks, and monitored for unusual traffic patterns or unexpected controller changes.