Network Detection and Response (NDR) Explained

  • Key Takeaways:
  • What does Network Detection and Response (NDR) do?
    NDR continuously analyzes network traffic, builds behavioral models to detect anomalies, and automates responses with AI.
  • How has NDR evolved from NTA?
    It shifted from basic traffic monitoring to advanced inspection and automated response using behavioral and signature analytics.
  • What key features does Stellar Cyber’s NDR offer?
    Deep packet inspection, distributed sensors, centralized data lake, AI-based threat detection, and automated SOAR integration.
  • How does Stellar Cyber reduce data volume and enhance detection?
    It achieves up to 500× data reduction while enriching with threat intel, enabling real-time AI-driven correlation and response.
  • How does NDR help unify security operations?
    Stellar Cyber’s NDR is integrated into Open XDR, enabling seamless correlation with SIEM, SOAR, and UEBA in one platform.

Network Detection and Response (NDR) adds new visibility into an organization’s networks by passively ingesting and analyzing internal network activity. With emerging LLMs and new demands made of network defense-in-depth, NDR tools are already evolving beyond this core capability. Gartner’s NDR report details how the tools in today’s market are pushing the boundaries with LLM augmentation, multimodal threat detection, and IaaS-based deployment.

The downstream impact of modern NDR is significant: more cohesive incident response, tighter analytics, and faster forensics. This guide is a comprehensive deep dive into NDR.

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How Does NDR Work

NDRs are unique in being able to continuously analyze network packets and traffic metadata that occurs within East-West traffic flows (internal) and between North-South (internal networks and the public internet). Each individual network action represents a key data point that is ingested by the NDR – each is then used to build a model of an internal network’s day-to-day behavior.

This allows any deviations to be detected immediately. These unnatural patterns are sent to analysts for further examination in the form of an alert; it’s here that the traffic is judged to be indicative of an attack, or harmless. Modern NDRs with automated response capabilities can automatically deploy a remedial action – like IP blocking – in response to a recognized threat. This keeps a network safe while the analyst determines its legitimacy.

The Evolution of NDR

NDR can trace its early roots back to Network Traffic Analysis (NTA). This older tool was jointly used by security and network administrators: it allowed them to keep tabs on which assets are receiving network traffic, how quickly each app or device is responding, and how much traffic is being sent to and from certain sources.

As the threat landscape evolved throughout the early 2010s, however, security admins found that network volume data didn’t tell the full story. Relying on NTA alone for threat detection demanded an exceedingly experienced and eagle-eyed network admin; it left a lot up to chance. Network Detection and Response emphasizes universal network data collection, alongside an added layer of analysis.

Today’s NDR tools strengthen this core behavioral analysis with file signature comparison and rule implementation. Once a potential threat is spotted, NDR can then automatically quarantine suspicious files, flag critical information to security admins, and correlate alerts within their wider security incidents.

What is the Role of NDR in Cybersecurity

Traditionally, organizations’ cybersecurity relied on static threat detection tools such as antivirus and firewalls: these would rely on signature-based detection, assessing the files being introduced into or shared across a network against the indicators of compromise within each tool’s database.

However, this setup – now referred to as perimeter-based cybersecurity – came with a few inherent flaws. For instance, if the firewall is not continuously updated, it’s possible for an attacker to slip through the gaps. Once a single device or service is compromised, the inherent trust between devices on an internal network is then exploited, as the attacker begins privilege escalation.

NDRs take advantage of this attack chain and recognize that almost every attack touches at least one internal network. Cybersecurity teams can deploy an NDR solution across both North-South and East-West traffic – granting them visibility into the traffic coming into the organization, and being shared between internal devices respectively. This shuts down one of the biggest footholds that attackers rely on. Our NDR Buyers Guide details how this traffic data is handled and analyzed for possible malicious activity.

What is the Role of NDR in the Security Operations Center (SOC)?

The modern SOC needs to be everywhere at once: with the sprawl inherent in modern networks, that is no mean feat. As a result, NDR plays a major role in today’s efficient SOCs, as it’s a centralized detection platform. The following capabilities can be delivered to a SOC by a suitable NDR.

Complete network visibility

A core component to a SOC is its ability to detect and respond to threats along the full spectrum of devices, users, and services. Network data is a valuable source of intelligence, but triage specialists and threat hunters are often slowed by its sheer quantity. NDR architecture allows it to automatically gather packet, flow, and log data from network infrastructure and firewalls. It also analyzes encrypted traffic, without needing to intercept it. This allows in-depth analysis to incorporate a greater breadth of sources, thereby lending the SOC a more comprehensive view of their networks.

Connected Alerts

Triage specialists play a key role in handling security alerts by gathering raw data and analyzing incoming alarms. Their responsibilities include validating alerts, assessing or adjusting their severity, and enriching them with contextual information. Modern NDRs accelerate this by integrating with other security tools, and automatically flagging network anomalies within their wider context – from phishing emails to suspicious file downloads.

Rapid Network Awareness

SOC managers are aware of how in-depth network expertise is a necessity. This demand can make hiring and training new SOC team members difficult and time-consuming. With NDR in SOC, even new team members lacking network expertise can deploy an NDR solution and begin to identify threats.

Rapid Network Response

The analytical power of NDR is offered to analysts in an intuitive dashboard. This user interface allows for alerts to be prioritized automatically, and allows manual network response capabilities to begin far sooner.

NDR vs Endpoint Detection and Response (EDR)

Modern cybersecurity demands visibility into more than just network activities – EDR is the corresponding solution that focuses on endpoint behavior. Network vs endpoint detection is fairly simple: in the same way that NDR ingests each action on a network and places it along a wider trend graph, EDR takes each device-level action and analyzes it in relation to its historical or role-specific behavior.

EDR products are typically delivered via a deployable endpoint agent on each endpoint. By having a local presence, EDR can ingest process information, which helps identify potentially malicious programs by monitoring what processes are running on the system. File information is also examined to validate the integrity of files, whilst user information verifies each account’s legitimacy. Finally, system information is gathered to maintain a comprehensive view of endpoint health.

Rather than NDR vs EDR, most organizations deploy NDR alongside EDR – this allows for the tracking and monitoring of a complete attack chain. From initial account compromise to network-level privilege escalation and eventual malware deployment, the entirety of complex attacks can be caught ahead of time. Seeing the potential of this, some cybersecurity vendors have started offering another layer of analysis and orchestration between the two – extended detection and response (XDR).

How Does NDR Compare with EDR and XDR?

NDR, EDR, and XDR are subtly distinct technologies, each targeting different facets of the threat identification and response processes. They also have different scopes – from network-specific to the organization’s entire attack surface.

NDR (Network Detection and Response)

EDR (Endpoint Detection and Response)

XDR (Extended Detection and Response)
Scope Network traffic. Endpoints (laptops, servers, devices). All (endpoints, network, cloud).
Primary Data Sources Network metadata, traffic flows. Endpoint telemetry, file, and process behavior. Aggregated telemetry across multiple domains.
Response Capabilities Limited to network-level actions, increasingly offering automated response. Isolated to endpoint-specific responses, such as quarantining. Offers complete freedom of cross-platform automated response.
Deployment Complexity Medium (requires network integration). Medium (requires agent installation on endpoints). High (requires integration across all security platforms, or primary data sources).
Best Use Case Detecting lateral movement, stealthy threats. Identifying compromised endpoints. Comprehensive threat detection and response.

Techniques Used in NDR Solutions

Since NDRs are continuously handling and analyzing such large quantities of data, it’s important to understand the different strategies they employ against complex threats.

Encrypted Traffic Analysis

Securing encrypted traffic has traditionally been a thorny topic: and with the vast majority of today’s traffic now encrypted, being unable to adequately analyze encrypted traffic can be a major oversight. However, decrypting all network packets mid-transfer can drastically increase the risk of data and token exposure.

To work around this, market-leading tools often rely on a stack of NDR techniques. To prevent token or decrypted data leaks, sensors can be deployed behind proxy servers. This employs encrypted traffic detection, and routes it via a proxy: the traffic is decrypted as normal, and the sensors then relay all intel to the central NDR engine. Learn more about our NDR capabilities here.

If proxy servers aren’t right for a specific use case, it’s possible to accurately detect a traffic’s legitimacy through its patterns. Fully-encrypted traffic can be assessed for malware through JA3 fingerprinting, without breaking their encryption. Furthermore, patterns and metadata can combine to detect the intent behind an encrypted packet, as the sensor can still extract the server certificate, IP addresses, domain names, session duration, and byte counts from the packet header and TLS/SSL handshaking.

Finally, if traffic decryption is fully necessary, modern NDRs can integrate with packet decryption services. The resulting network data is then sent to the central analysis engine as normal.

Automated Asset Discovery

Knowing which devices are transferring data into and out of a network is vital. NDRs automatically track and add assets to the asset management dashboard, according to each one’s corresponding MAC address, IP address and host name. This then allows network-level risks to be displayed according to their impacted assets.

Protocol Decoding

Network protocols are established sets of rules that define how data is formatted, transmitted, received, and interpreted between devices on a network. These are vital pieces of the contextual puzzle; as such, NDRs essentially rebuild the raw data they have to determine the appropriate protocol. They then compare the real-world network data against this expected protocol, allowing for rapid detection of any traffic deviation. `

Behavioral Analysis

Alongside the protocols behind each traffic flow, NDRs are able to build a model of how each network operates day-to-day. Over several months, for instance, it may see an employee upload to a specific site over SFTP at 10am. When all of a sudden that employee uploads a file to 5 other internal devices at 2am, it knows to flag this suspicious action for further analysis.

How to Deploy Network Detection and Response

An NDR’s deployment needs to cover all networks your organization relies on – whether that’s cloud-based, fully on-prem, or a mix of the two. The following deployment methods should give you an up-close view of how NDRs are technically deployed within an organization.

Sensor Deployment

NDR requires sensors to be deployed within any network being monitored. There are specific sensors for different use cases, however, and successful deployment demands the correct one for the job. For instance, Linux distribution environments need a Linux server sensor. These are often deployed with a preset amount of available CPU resources it can use at any one time, in order to protect server quality while collecting command executions and logs. Windows servers demand their own type of sensor, too; these collect the full extent of Windows event types.

Modular sensors are yet another type: these allow for customizable features to be packaged along with the sensor. For instance, this can include Log Forwarding – should there be a need to deploy with a SIEM or other security tool – and Network Traffic ingestion – as required by the NDR. For more heavy-duty security requirements, modular sensors can also be deployed with sandbox and intrusion detection systems.

With the correct sensors identified for each deployment, it’s important to set them up accordingly. A whole host of deployment methods are available for this: a SPAN port is one of the most common, and it works by mirroring network traffic on a network switch to the port with the NDR sensor. This allows the NDR tool to passively packet capture all traffic going to that port.

Virtual environments rely on virtual taps being deployed, which capture copies of the data flowing between VMs inside the host; physical TAPs miss this traffic, since it never traverses physical network cables. The network activity of remote endpoints can be monitored with agent-based collectors; lightweight collectors that install directly onto a device.

Data Ingestion

With all data continuously monitored by sensors, it then needs to be ingested and analyzed by the NDR’s central analysis engine. This is conducted by two processes: receivers and connectors. The former is a running task that takes sensor input and disseminates it between the IP addresses or port numbers being contacted – and the latter looks at the associated raw network packet data.

Download and Setup

Downloading and configuring the NDR management console depends on the provider that’s been picked – but all should require an initial establishment of administrator roles, alert thresholds, and notification protocols. A week or two of training is usually a minimum requirement when a new tool is first deployed; this helps nail down how it integrates with analysts’ workflows.

Enable and Tune Automated Responses

Automated responses are a key capability of modern NDR tools: they also represent a significant time save against potential attacks. Depending on the NDR, its automated response actions such as TCP session termination, dynamic network segmentation, or traffic throttling need to be configured – alongside the behavior profile that needs to trigger each action. Learn more on how to deploy an NDR here.

Integrating NDR with Other Security Tools

NDR’s ability to build heuristic models of normal network behavior – and therefore spot any deviations from it – greatly complements intel brought forward by other security technologies. If these can be integrated, a network-level awareness can be introduced into each alert. The following security tools are those that see common and successful NDR integrations.

EDR

By integrating EDR with NDR, it’s possible to gain not only a complete understanding of the attack chain – but also to automatically respond to threats through the EDR device. For instance, when malware is linked back to a device, a joint EDR/NDR solution can automatically isolate it from the network. This containment prevents the threat from spreading, while giving security teams the opportunity to investigate the incident and apply necessary remediation measures.

SIEM

SIEMs are ubiquitous in security teams – they allow for log analysis and detection, and are the predecessors to modern threat management. However, because SIEMs handle so many logs – and logs alone don’t give the most in-depth threat visibility – SIEMs are highly prone to false positives. The result is thousands of alerts a day, which are functionally impossible to manually review.

NDRs allow for a layer of authentication to be established – whenever the SIEM spots a potential incident, the corresponding network data can be analyzed. Should both data sources point to an attack, the alert can be issued via the NDR’s central dashboard. This not only helps filter out incorrect alerts, but also gives the reviewing analyst a better foundation to work off.

Firewalls

NDR enhances firewall threat intelligence by detecting unusual or malicious network behavior. Since it traces the behavior to a specific IP address, this real-time intel can then be shipped to the firewall that’s deployed around each network, or sub-network. This then automatically builds and enforces a relevant policy, blocking the suspicious traffic.

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