Understanding what NDR (Network Detection and Response) is means understanding where many of today’s most dangerous threats hide: in network traffic, often invisible to antivirus tools and endpoint agents. NDR analyses flows in real time, detects anomalous behaviour and enables automated responses, closing an increasingly evident visibility gap across IT, OT and IoT environments.
NDR: definition and differences from other monitoring tools
Network Detection and Response refers to a category of tools that continuously monitor network traffic without agents installed on endpoints. This is the key difference from EDR, which protects individual devices, and from SIEM, which correlates logs already generated by other sources. A firewall operates on predefined rules: it blocks what it recognises, but it does not detect anomalous behaviour in internal traffic flows. Meanwhile, attacks increasingly move inside the network (east-west traffic, lateral movement), exactly where firewalls and perimeter controls do not look. And in industrial settings, a cyber incident can have physical consequences on production.
How NDR analyses network traffic in modern environments
- Passive traffic analysis: the NDR sensor receives a copy of network traffic (SPAN/mirror port or TAP) passively, without installing agents on endpoints or affecting network performance. This is essential in OT environments, where installing an agent on a PLC is simply not feasible.
- Deep packet inspection: packet inspection identifies protocols, applications and commands, including industrial ones. On encrypted traffic, analysis relies on metadata (TLS handshakes, certificates, volumes, periodicity) to spot beaconing and anomalous channels without decrypting the content.
- Behavioural baselining: the system builds a statistical model of normal traffic for each host and segment. Significant deviations generate an alert, ideally before the damage spreads.
- Real-time anomaly detection: by comparing each traffic flow against the baseline, NDR identifies lateral movement, data exfiltration and command-and-control communications, activities that map to MITRE ATT&CK tactics (Lateral Movement, Exfiltration, Command and Control).
Why automated response is critical in IT, OT and IoT networks
In an industrial network, even a few minutes’ delay in responding to an incident can translate into production downtime. When IoT devices and OT systems communicate using proprietary protocols and intermittent connectivity, a human operator cannot react quickly enough. Automated response enables a compromised segment to be isolated without disrupting adjacent processes: production continues while the risk is contained. Even when connectivity is degraded, response logic remains operational locally, ensuring protection without relying on a remote control centre. In OT, however, response must be calibrated: the most mature platforms let you start in observation-only mode and enable automated actions gradually, segment by segment.
Extended visibility, reduced risk and business continuity: tangible benefits
- Coverage of devices where agents cannot be deployed: OT devices, IoT devices and legacy systems are monitored without installing software, reducing structural blind spots.
- Reduced dwell time: real-time behavioural detection reduces the number of days an attacker remains within the network, limiting the time available to cause damage.
- Direct support for compliance: continuous visibility feeds audit trails and the incident detection and notification (24h/72h) required by NIS2. For manufacturers of devices subject to the Cyber Resilience Act, whose reporting obligations apply from 11 September 2026, NDR provides evidence that helps reconstruct incidents.
- Resilience even when offline: with on-premises sensors, local response does not depend on cloud connectivity, ensuring protection even in environments with unstable network infrastructure.
Typical use cases: hybrid and distributed environments, and critical infrastructure
| Sector / Scenario | Main challenge | Specific value of NDR |
|---|---|---|
| Manufacturing and legacy OT | Industrial protocols that EDR cannot handle; production lines operating around the clock | Passive, agentless visibility; local isolation of the compromised segment without stopping the process |
| Smart cities and intelligent infrastructure | Networks distributed across large geographical areas; variable or intermittent connectivity | Autonomous operation even when offline; anomaly detection without a connection to the control centre |
| Public sector and public administration | Distributed architectures; stringent governance and privacy requirements | Support for NIS2 compliance through visibility into internal traffic, without exposing data outside the perimeter |
| Hybrid IT/OT/IoT networks | Mixed environments with heterogeneous devices and legacy systems that cannot be patched | Agentless coverage of nodes on monitored segments, including devices that cannot be managed using traditional software |
NDR, SOC and SIEM: how they integrate into incident response processes
The SIEM collects logs and the SOC interprets them: both depend on the quality of the incoming telemetry. NDR closes the network traffic blind spot by enriching the data stream with behavioural evidence that logs alone cannot provide. The practical result is more accurate alert prioritisation: analysts receive signals that already have context, spend less time on false positives and make containment decisions faster. Measurable detection capability is also one of the factors cyber insurers increasingly assess when evaluating an organisation’s risk profile.
Frequently asked questions about NDR
What is the main difference between NDR, EDR and SIEM?
EDR protects the individual endpoint it is installed on, SIEM centralises and correlates logs, and NDR analyses traffic between devices. They are complementary: NDR covers what the other two cannot see, namely devices without agents and movements inside the network.
How does NDR monitor OT and IoT devices without installing software on them?
It works on a copy of the traffic, received from a SPAN port or TAP, without interacting with the devices. It is the only practical approach for PLCs, sensors and legacy systems that cannot run agents or cannot be modified.
Why is automated response so important in industrial networks?
Because it shortens the time between detection and containment, limiting propagation and the risk of plant downtime. In OT it should be introduced gradually, starting with observation and defining which segments can be isolated automatically.
How does NDR support compliance with NIS2 and the Cyber Resilience Act?
For NIS2, it provides continuous detection, traceability and data for incident notification within 24 and 72 hours. The CRA mainly concerns manufacturers of products with digital elements: NDR does not replace their obligations, but helps collect evidence on incidents.
How does NDR improve the work of SOC analysts?
It adds network context to the SIEM: who communicated with whom, when and with what volumes. Alerts arrive already correlated, with fewer false positives and shorter investigation times.
