Network Detection and Response (NDR) Explained

Key Takeaways

• EDR watches individual endpoints. NDR watches the traffic between them, including devices that can’t run an agent at all.

• CISA’s own 2024 red-team advisory found a real critical infrastructure organization relied too heavily on EDR and missed attacker activity that network-layer monitoring would have caught. 

• Vulnerability exploitation, much of it against edge devices and VPNs invisible to EDR, overtook stolen credentials as the top cause of breaches for the first time in 2026.

• The realistic answer for most mid-market organizations is not NDR instead of EDR. It’s NDR added to close what EDR structurally cannot see.

What Is NDR (Network Detection and Response)? 

NDR is a category of security tooling that analyzes network traffic to detect threats, rather than relying on software installed on individual devices. It inspects north-south traffic (in and out of the network) and east-west traffic (movement between systems inside it), looking for behavior that indicates compromise rather than matching known-bad signatures. 

That distinction, behavior over signatures, is why NDR catches things signature-based tools miss. A device moving laterally at 2 a.m., authenticating to systems it’s never touched before, or exfiltrating data at an unusual volume, looks abnormal on the network even when nothing about the traffic matches a known malware signature. 

NDR vs EDR: What’s the Actual Difference? 

Quick answer: EDR monitors what happens on a device. NDR monitors what happens between devices. EDR requires an agent installed on the endpoint. NDR does not, it watches the network itself, which means it can see activity involving devices that can never run an agent at all: firewalls, routers, VPN appliances, IoT sensors, OT equipment, and unmanaged personal devices. 

Neither tool replaces the other. The realistic architecture for most mid-market organizations layers both: EDR for the devices that can run it, NDR for the network activity and the infrastructure that can’t. 

Why This Gap Usually Surfaces After an Incident 

This isn’t a hypothetical risk. It’s a documented one. In November 2024, CISA published the results of a red-team engagement it conducted at a real US critical infrastructure organization’s request. The finding, in CISA’s own words: the organization “relied too heavily on host-based endpoint detection and response (EDR) solutions and did not implement sufficient network layer protections.” 

The details are worth sitting with. The red team gained access through an internet-facing web server, moved through the organization’s DMZ, and ultimately compromised its domain controller. In one instance, EDR did work as designed, it generated an alert on the initial phishing payload. Nobody read it. In another, the red team simply inflated its file size past the EDR’s upload threshold and walked past detection entirely. 

The broader pattern behind that single case is now showing up in industry-wide data. Verizon’s 2026 Data Breach Investigations Report, analyzing more than 22,000 confirmed breaches, found that vulnerability exploitation overtook stolen credentials as the leading cause of breaches for the first time in the report’s 19-year history, rising to 31% of breaches. Edge devices and VPNs specifically, infrastructure that by design cannot run an EDR agent, went from 3% to 22% of exploitation-driven breaches in a single year. 

That’s the pattern behind the ICP this piece is written for. The gap doesn’t usually get discovered in a planning meeting. It gets discovered when something moves through the network and the tool everyone was relying on never saw it happen. 

What to Look for in Network Detection Response Tools 

Not every product marketed as NDR delivers the same coverage. Before evaluating options, confirm: 

Where Does a Managed Provider Fit? 

Network-layer monitoring is continuous work, tuning detection to your specific environment, triaging alerts, and investigating what’s real. Very few mid-market IT teams can staff that as a dedicated function on top of everything else on their plate. 

What a provider should take on is the continuous piece: monitoring traffic, tuning detection thresholds to your environment, and triaging alerts before they reach you. What should stay with you is context, which systems are genuinely sensitive and which network paths a real business process explains versus one nobody can account for. 

Our Security as a Service covers continuous monitoring and detection, and our Managed Cloud and IT service includes 24/7 monitoring of administrative changes, firewall rule drift, and authentication alerts through our certified SOC, the network-layer visibility this piece is about.  

FAQs 

1 Is NDR the same thing as a firewall or IDS/IPS? 

No. A firewall and IDS/IPS largely rely on rules and known signatures to block or flag traffic. NDR uses behavioral analysis to detect anomalies that don’t match any known signature, which is what lets it catch novel and living-off-the-land attacks that rule-based tools miss. 

2 Do we need NDR if we already have EDR everywhere? 

If every device on your network can run an agent, you have narrowed the gap, but not closed it. EDR still can’t see traffic between devices, and most environments have at least some infrastructure, firewalls, VPN appliances, IoT devices, that can never run an agent at all. 

3 Can NDR see inside encrypted traffic? 

Modern NDR tools generally don’t need to fully decrypt traffic to detect threats. They analyze behavioral metadata, connection patterns, timing, volume, and destinations, which remains visible even when the payload itself is encrypted. 

4 How is NDR different from XDR? 

XDR (extended detection and response) aims to correlate data across endpoint, network, and other sources into a single platform. NDR is one of the data sources XDR pulls from. Some XDR platforms include strong network coverage; others rely on partner integrations, so it’s worth confirming what’s actually native versus bolted on.