Detections

Real-time monitoring identifies NetFlow showing a source making sequential connections to multiple field device Internet Protocol (IP) addresses, each resulting in large response payloads characteristic of directory listing rather than value reads. OT operational-fidelity gate: Do not alert on novelty, scan/read volume, or enumeration alone. Alert when the source role is not authorized for discovery/polling and the target scope, address/tag range, protocol, or rate deviates from the established operational baseline. Suppress normal SCADA/HMI/historian polling, commissioning, asset inventory, backup, diagnostics, and approved engineering activity.

Real-time monitoring identifies a new device appearing on the Industrial Control System (ICS) network with network behavior consistent with an ICS master station, with a Media Access Control (MAC) address not in the approved device inventory. OT operational-fidelity gate: Alert only when the master/station identity or source is not authorized for the target device and command function, or when a normally authorized master violates its configured role/sequence and produces a corroborating device/process-state change. Suppress legitimate redundancy/failover, hot-standby promotion, commissioning, and approved engineering master activity.

Real-time monitoring identifies transfer protocol traffic such as the Trivial File Transfer Protocol (TFTP) or vendor-specific protocol traffic initiating firmware-update mode on Industrial Control System (ICS) device Internet Protocol (IP) addresses from sources not in the approved engineering workstation list. OT operational-fidelity gate: Alert only when the action is not attributable to an authorized operator/engineering source for the specific target and function, and it is either outside an approved change/maintenance window or lacks matching change-control context; where telemetry permits, require corroborating device, configuration, or process-state effect. Suppress activity that fully matches approved maintenance, commissioning, failover, recovery, or tested control procedures.

Real-time monitoring identifies new east-west connections between Industrial Control System (ICS) hosts on remote service ports not in the approved communication matrix. OT operational-fidelity gate: Alert only when the account/device/session violates the approved identity + source host/jump path/zone policy and is corroborated by access to a protected OT asset, execution, configuration change, or another security-relevant follow-on event. Suppress approved shift activity, vendor support, break-glass use, commissioning, and documented remote-access windows.

Real-time monitoring identifies a host generating rapid, sequential Transmission Control Protocol (TCP) connection attempts across multiple destination ports on Industrial Control System (ICS) device Internet Protocol (IP) addresses, targeting ICS-specific protocol ports, from a source not in the approved control server inventory. OT operational-fidelity gate: Do not alert on novelty, scan/read volume, or enumeration alone. Alert when the source role is not authorized for discovery/polling and the target scope, address/tag range, protocol, or rate deviates from the established operational baseline. Suppress normal SCADA/HMI/historian polling, commissioning, asset inventory, backup, diagnostics, and approved engineering activity.

Real-time monitoring identifies network device management session authentication such as Secure Shell (SSH), Remote Authentication Dial-In User Service (RADIUS), and Terminal Access Controller Access-Control System Plus (TACACS+) using valid Industrial Control System (ICS) network administrator credentials but originating from source IPs outside the approved Network Management System (NMS) Classless Inter-Domain Routing (CIDR) subnet or at times inconsistent with the account's normal usage pattern, where the session performs configuration changes not reflected in any open change-control ticket. OT operational-fidelity gate: Alert only when the account/device/session violates the approved identity + source host/jump path/zone policy and is corroborated by access to a protected OT asset, execution, configuration change, or another security-relevant follow-on event. Suppress approved shift activity, vendor support, break-glass use, commissioning, and documented remote-access windows.

Use an OT-capable protocol decoder to monitor SNMP requests/responses and identify access to vendor-internal or undocumented OIDs from sources outside the approved NMS inventory, especially SET operations or unusual walks against control-network infrastructure. This is network-protocol observation, not OS API execution; require decoded SNMP transaction content or equivalent packet inspection.

Real-time monitoring identifies Simple Network Management Protocol (SNMP) walk requests, Cisco Discovery Protocol (CDP)/Link Layer Discovery Protocol (LLDP) enumeration frames, or Internet Control Message Protocol (ICMP)-based traceroute sequences from an Industrial Control System (ICS) host that has not previously generated management-protocol traffic. OT operational-fidelity gate: Do not alert on novelty, scan/read volume, or enumeration alone. Alert when the source role is not authorized for discovery/polling and the target scope, address/tag range, protocol, or rate deviates from the established operational baseline. Suppress normal SCADA/HMI/historian polling, commissioning, asset inventory, backup, diagnostics, and approved engineering activity.

Real-time monitoring identifies Industrial Control System (ICS) network device telemetry gaps -- Simple Network Management Protocol (SNMP) polling returning inconsistent results, syslog sequence gaps -- suggesting kernel-level manipulation of device-reported state. OT operational-fidelity gate: Alert only when execution violates an approved signer/hash/path/parent/process or tool allowlist, or originates from an unauthorized user/tool, and is tied to an OT asset or follow-on OT-relevant action. Suppress vendor-signed software, approved engineering utilities, diagnostics, patching, backup, and documented maintenance.

Real-time monitoring identifies Simple Network Management Protocol (SNMP) GET requests targeting system information Object Identifiers (OIDs) from a source not in the approved Network Management System (NMS) Classless Inter-Domain Routing (CIDR) subnet, directed at Industrial Control System (ICS) server or device IPs. OT operational-fidelity gate: Do not alert on novelty, scan/read volume, or enumeration alone. Alert when the source role is not authorized for discovery/polling and the target scope, address/tag range, protocol, or rate deviates from the established operational baseline. Suppress normal SCADA/HMI/historian polling, commissioning, asset inventory, backup, diagnostics, and approved engineering activity.

Real-time monitoring identifies Simple Network Management Protocol (SNMP) SET commands to power Management Information Base (MIB) restart Object Identifiers (OIDs) or Command Line Interface (CLI) reload commands from a source not in the approved Network Management System (NMS) Classless Inter-Domain Routing (CIDR). OT operational-fidelity gate: Alert only when the action is not attributable to an authorized operator/engineering source for the specific target and function, and it is either outside an approved change/maintenance window or lacks matching change-control context; where telemetry permits, require corroborating device, configuration, or process-state effect. Suppress activity that fully matches approved maintenance, commissioning, failover, recovery, or tested control procedures.

Real-time monitoring identifies a network-device ACL, filter, or rate-limit policy change that suppresses or blocks ICS alarm-notification traffic outside the approved network-change baseline. OT operational-fidelity gate: Alert only when the action is not attributable to an authorized operator/engineering source for the specific target and function, and it is either outside an approved change/maintenance window or lacks matching change-control context; where telemetry permits, require corroborating device, configuration, or process-state effect. Suppress activity that fully matches approved maintenance, commissioning, failover, recovery, or tested control procedures.

Real-time monitoring identifies a network infrastructure device exhibiting behavioral anomalies (unexpected listening ports, new routing entries) after a vendor firmware update or hardware replacement, where the device firmware hash does not match the authorized inventory. OT operational-fidelity gate: Alert only when execution violates an approved signer/hash/path/parent/process or tool allowlist, or originates from an unauthorized user/tool, and is tied to an OT asset or follow-on OT-relevant action. Suppress vendor-signed software, approved engineering utilities, diagnostics, patching, backup, and documented maintenance.

Real-time monitoring identifies a new device connecting to an Industrial Control System (ICS) network switch port that was previously unused or previously assigned to a different device Media Access Control (MAC) address immediately following physical access to the environment, with subsequent Industrial Control System (ICS) protocol traffic to field devices. OT operational-fidelity gate: Alert only when the account/device/session violates the approved identity + source host/jump path/zone policy and is corroborated by access to a protected OT asset, execution, configuration change, or another security-relevant follow-on event. Suppress approved shift activity, vendor support, break-glass use, commissioning, and documented remote-access windows.

Real-time monitoring identifies network device management commands succeeding from a source not in the approved Network Management System (NMS) Classless Inter-Domain Routing (CIDR) subnet, following exploit-pattern traffic to the device's management interface, suggesting exploitation of a management-plane vulnerability to gain elevated access without valid credentials. OT operational-fidelity gate: Alert only when execution violates an approved signer/hash/path/parent/process or tool allowlist, or originates from an unauthorized user/tool, and is tied to an OT asset or follow-on OT-relevant action. Suppress vendor-signed software, approved engineering utilities, diagnostics, patching, backup, and documented maintenance.

Real-time monitoring identifies Industrial Control System (ICS) network device syslog showing a gap in expected event sequence numbers, or syslog forwarding interruption from a device coinciding with a period of suspicious activity on that device. OT operational-fidelity gate: Alert only when execution violates an approved signer/hash/path/parent/process or tool allowlist, or originates from an unauthorized user/tool, and is tied to an OT asset or follow-on OT-relevant action. Suppress vendor-signed software, approved engineering utilities, diagnostics, patching, backup, and documented maintenance.

Real-time monitoring identifies authentication attempts against Industrial Control System (ICS) network device management interfaces using well-known default vendor credentials from source Internet Protocol (IP) addresses not in the approved Network Management System (NMS) Classless Inter-Domain Routing (CIDR) subnet range. OT operational-fidelity gate: Alert only when the account/device/session violates the approved identity + source host/jump path/zone policy and is corroborated by access to a protected OT asset, execution, configuration change, or another security-relevant follow-on event. Suppress approved shift activity, vendor support, break-glass use, commissioning, and documented remote-access windows.

Real-time monitoring identifies an Industrial Control System (ICS) network device receiving a configuration erase command from a source not in the approved Network Management System (NMS) Classless Inter-Domain Routing (CIDR) subnet, or outside a change-control window. OT operational-fidelity gate: Alert only when the action is not attributable to an authorized operator/engineering source for the specific target and function, and it is either outside an approved change/maintenance window or lacks matching change-control context; where telemetry permits, require corroborating device, configuration, or process-state effect. Suppress activity that fully matches approved maintenance, commissioning, failover, recovery, or tested control procedures.

Real-time monitoring identifies Simple Network Management Protocol (SNMP) SET commands to service-stop Object Identifiers (OIDs) or Command Line Interface (CLI) commands stopping routing/switching processes critical to Industrial Control System (ICS) communication, from sources not in the approved Network Management System (NMS) Classless Inter-Domain Routing (CIDR) subnet. OT operational-fidelity gate: Alert only when the action is not attributable to an authorized operator/engineering source for the specific target and function, and it is either outside an approved change/maintenance window or lacks matching change-control context; where telemetry permits, require corroborating device, configuration, or process-state effect. Suppress activity that fully matches approved maintenance, commissioning, failover, recovery, or tested control procedures.

Real-time monitoring identifies network device credential changes such as Authentication, Authorization, and Accounting (AAA) password modification or Simple Network Management Protocol (SNMP) community string modification from a source not in the approved Network Management System (NMS) Classless Inter-Domain Routing (CIDR) subnet, corroborated by syslog showing authentication failures from legitimate NMS systems following the change. OT operational-fidelity gate: Alert only when the action is not attributable to an authorized operator/engineering source for the specific target and function, and it is either outside an approved change/maintenance window or lacks matching change-control context; where telemetry permits, require corroborating device, configuration, or process-state effect. Suppress activity that fully matches approved maintenance, commissioning, failover, recovery, or tested control procedures.

Real-time monitoring identifies remote console or web management sessions to Industrial Control System (ICS) network devices from IP addresses that are not approved Network Management System (NMS) hosts, where the sessions access device configuration interfaces. OT operational-fidelity gate: Alert only when the account/device/session violates the approved identity + source host/jump path/zone policy and is corroborated by access to a protected OT asset, execution, configuration change, or another security-relevant follow-on event. Suppress approved shift activity, vendor support, break-glass use, commissioning, and documented remote-access windows.

Real-time monitoring identifies ACL modifications on Industrial Control System (ICS) network devices specifically blocking ICS reporting message ports while allowing command ports to remain open. OT operational-fidelity gate: Alert only when the action is not attributable to an authorized operator/engineering source for the specific target and function, and it is either outside an approved change/maintenance window or lacks matching change-control context; where telemetry permits, require corroborating device, configuration, or process-state effect. Suppress activity that fully matches approved maintenance, commissioning, failover, recovery, or tested control procedures.

Real-time monitoring identifies Industrial Control System (ICS) network device syslog recording unexpected restarts or crashes coinciding with anomalous traffic patterns on management interfaces. OT operational-fidelity gate: Alert only when execution violates an approved signer/hash/path/parent/process or tool allowlist, or originates from an unauthorized user/tool, and is tied to an OT asset or follow-on OT-relevant action. Suppress vendor-signed software, approved engineering utilities, diagnostics, patching, backup, and documented maintenance.

Real-time monitoring identifies configuration changes to serial server or terminal server devices that alter serial port parameters for ports connected to field devices. OT operational-fidelity gate: Alert only when the action is not attributable to an authorized operator/engineering source for the specific target and function, and it is either outside an approved change/maintenance window or lacks matching change-control context; where telemetry permits, require corroborating device, configuration, or process-state effect. Suppress activity that fully matches approved maintenance, commissioning, failover, recovery, or tested control procedures.

Real-time monitoring identifies a new device on the Industrial Control System (ICS) network placing its Network Interface Card (NIC) in promiscuous mode, detectable by anomalous broadcast traffic handling or unauthorized Switched Port Analyzer (SPAN) session requests on managed switches. OT operational-fidelity gate: Do not alert on novelty, scan/read volume, or enumeration alone. Alert when the source role is not authorized for discovery/polling and the target scope, address/tag range, protocol, or rate deviates from the established operational baseline. Suppress normal SCADA/HMI/historian polling, commissioning, asset inventory, backup, diagnostics, and approved engineering activity.