In the humid air of Houston, Texas, a chemical plant is preparing to deploy a...

TCP port 102 is strongly associated with Siemens S7 communications, commonly referred to as S7comm, which is used by Siemens SIMATIC S7 PLC families and related engineering and HMI components in OT environments. In CEH coverage of ICS and SCADA reconnaissance, identifying industrial protocols by their well-known ports is a standard first step because it quickly narrows down device type, vendor ecosystem, and likely attack surface. When Ethan targets TCP 102 and the scan reveals PLC models used in the automation process, that aligns directly with enumerating Siemens SIMATIC S7 PLCs, since S7comm typically operates over ISO-on-TCP on port 102.

The other options do not match the port-protocol pairing described. Modbus TCP most commonly uses TCP port 502, so “scanning Modbus devices” would be associated with 502 rather than 102. “Capturing Modbus TCP traffic using Wireshark” is passive sniffing and also would focus on Modbus traffic patterns on 502, not an active Nmap sweep on 102. Omron PLCs may use different protocols and ports depending on model and configuration, but TCP 102 is the canonical indicator for Siemens S7 in most defensive and offensive playbooks taught for OT discovery.

From a defensive perspective, CEH-aligned best practices emphasize segmenting OT networks, restricting access to engineering ports like 102, monitoring for scanning behavior, and enforcing allowlisted communications between SCADA, HMIs, and PLCs to reduce the risk of unauthorized enumeration and follow-on manipulation.