The Definitive Guide to Agentless Network Detection
Why passive network monitoring is the only viable security approach for critical infrastructure, OT systems, and legacy environments
Critical infrastructure requires security that doesn't compromise operational integrity
When a hospital's MRI machine, a power plant's SCADA system, or a factory's robotic assembly line needs protection, traditional endpoint security isn't an option. These systems can't run software agents, can't be rebooted for updates, and can't tolerate any performance impact. Agentless network detection isn't just a preference for these environments—it's the only viable approach.
Introduction: The Agent Problem
For years, endpoint security has dominated the cybersecurity conversation. Install an agent on every device, and you gain visibility and control. But this approach makes a dangerous assumption: that you can install an agent on every device.
In reality, most enterprise networks contain significant portions that are fundamentally incompatible with agent-based security:
- Legacy systems running obsolete operating systems
- Industrial equipment with real-time constraints
- Medical devices requiring FDA certification
- IoT sensors with limited compute resources
- Third-party managed systems you can't modify
These "unagentable" assets often include your most critical systems—and they're increasingly targeted by attackers who know they're less protected.
Agent vs Agentless Architecture
Understanding the fundamental differences between these approaches is essential for choosing the right security architecture.
Agent-Based Security
Software installed on each endpoint that monitors system activity, blocks threats, and reports to a central console. Examples include EDR (Endpoint Detection and Response), antivirus, and host-based IDS.
Agentless Network Detection
Analysis of network traffic to detect threats without installing software on endpoints. Works by monitoring network flows, inspecting packets, and analyzing communication patterns. Examples include NDR (Network Detection and Response) and network-based IDS.
| Aspect | Agent-Based | Agentless |
|---|---|---|
| Deployment | Install on each device | Network tap or mirror port |
| Coverage | Only devices with agents | All network traffic |
| Performance Impact | CPU/memory on endpoints | None on endpoints |
| Maintenance | Agent updates required | No endpoint maintenance |
| OT/IoT Support | Limited | Full visibility |
| Attack Surface | Agents add attack surface | Passive, minimal exposure |
| Encrypted Traffic | Full visibility (on host) | Metadata and behavior analysis |
Industrial systems require security that doesn't interfere with real-time operations
Why Agentless Matters
Agentless network detection offers compelling advantages beyond just covering "unagentable" devices:
1. Zero Operational Risk
Agent crashes, conflicts, and performance issues have caused production outages across industries. Agentless monitoring is completely passive—it cannot affect the systems it monitors. For environments where uptime is measured in nines, this is non-negotiable.
2. Immediate Deployment
No software rollout, no compatibility testing, no change management processes. Connect to a network tap or SPAN port and start monitoring immediately. What takes months with agents takes hours with agentless.
3. Universal Coverage
Network traffic reveals all connected devices—even those you don't know about. Shadow IT, rogue devices, and forgotten systems all become visible. You can't protect what you can't see.
4. Tamper-Proof Visibility
Attackers routinely disable endpoint agents as their first action after gaining access. Network-based detection continues to see their activity because it operates outside the compromised system.
5. Reduced Attack Surface
Every agent is a potential vulnerability. Agent software has been exploited in major breaches. Agentless monitoring adds no software to endpoints and therefore adds no exploitable code.
Agentless security isn't about choosing between agents and network monitoring—it's about ensuring you have visibility where agents can't go, which is often where your most critical assets reside.
Critical Infrastructure Use Cases
Healthcare
Medical devices—MRI machines, infusion pumps, patient monitors—run embedded systems that cannot be modified without FDA recertification. Agentless NDR provides visibility into these devices' network behavior, detecting compromises without touching the devices themselves. Learn more about protecting legacy and medical systems.
Manufacturing
Industrial control systems (ICS) and SCADA networks control physical processes that cannot tolerate interruption. PLCs, HMIs, and robotic controllers operate on real-time constraints incompatible with security agents. Network monitoring protects these systems while they continue operating.
Energy and Utilities
Power grids, water treatment plants, and gas pipelines rely on operational technology that predates modern security concerns. Many run Windows XP or proprietary operating systems. Agentless detection is the only practical security option.
Transportation
Air traffic control, rail signaling, and maritime systems have certification requirements that preclude software modifications. Network-based monitoring provides security assurance without affecting certified systems.
Financial Services
Trading systems, ATM networks, and payment processing infrastructure have strict performance requirements. Agentless monitoring provides security visibility without latency impact.
Medical devices require FDA-certified configurations that cannot accommodate security agents
How Agentless Detection Works
Modern agentless network detection uses sophisticated analysis techniques to achieve high-fidelity threat detection:
Traffic Collection
Network traffic is captured via SPAN ports, network TAPs, or cloud VPC flow logs. The collection is entirely passive—the security system observes traffic but doesn't modify or interrupt it.
Flow Analysis
NetFlow, IPFIX, or similar protocols provide metadata about network connections: source/destination IPs, ports, protocols, data volumes, and timing. This metadata reveals communication patterns without requiring deep packet inspection.
Behavioral Modeling
AI models learn normal behavior patterns for your network: which devices communicate with which others, how much data they exchange, and when. Deviations from these baselines indicate potential threats.
Protocol Analysis
Deep packet inspection where appropriate reveals application-layer activity: DNS queries, HTTP requests, industrial protocols (Modbus, DNP3, OPC UA). This provides context for understanding what systems are actually doing.
Threat Intelligence Correlation
Network indicators (IP addresses, domains, TLS certificates) are correlated with threat intelligence to identify known malicious infrastructure. Combined with behavioral analysis, this catches both known and unknown threats.
The Encryption Challenge: Modern encryption means network monitoring can't see packet contents. But it can see everything else: who talks to whom, when, how much data moves, and communication patterns. These behavioral signals are often more reliable than content inspection—and attackers can't hide them without going silent entirely.
Detection Capabilities
Agentless network detection excels at identifying threats that span multiple systems:
Command and Control (C2)
C2 traffic has distinctive patterns: periodic beaconing, unusual destination countries, DNS tunneling, or domain generation algorithms. Network analysis detects these patterns regardless of the compromised device.
Lateral Movement
When attackers move through a network, they create new connection patterns: a workstation connecting to servers it never accessed before, unusual administrative protocols, or scanning activity. Network visibility makes lateral movement visible.
Data Exfiltration
Large data transfers to unusual destinations, encrypted connections to unknown services, or data leaving through unexpected channels all indicate potential exfiltration. Network monitoring catches these patterns.
Unauthorized Access
Connections from unexpected locations, access outside business hours, or authentication to sensitive systems from unusual sources all appear in network traffic.
Rogue Devices
New devices appearing on the network—whether unauthorized IoT, attacker implants, or shadow IT—become immediately visible through their network activity.
Protocol Anomalies
Industrial protocols being used in unexpected ways, application protocols over non-standard ports, or encrypted traffic where plain text is expected all signal potential compromise.
Implementation Guide
Deploying agentless network detection involves several key steps:
1. Network Assessment
- Identify key network segments requiring monitoring
- Map critical assets and their communication patterns
- Determine available collection points (SPAN, TAP, flow export)
- Assess bandwidth requirements for traffic collection
2. Collection Infrastructure
- Deploy network TAPs or configure SPAN ports on switches
- Enable NetFlow/IPFIX on routers and firewalls
- Configure cloud flow logs for cloud workloads
- Ensure collection points cover all critical segments
3. Sensor Deployment
- Install analysis sensors to receive collected traffic
- Configure sensors for appropriate traffic types
- Establish connectivity to management console
- Validate traffic visibility and coverage
4. Baseline Establishment
- Allow the system to learn normal traffic patterns
- Define asset criticality and custom policies
- Tune detection thresholds based on environment
- Validate against known good traffic
5. Operational Integration
- Integrate with SIEM for alert correlation
- Connect to SOAR for automated response
- Establish incident response procedures
- Train security team on new capabilities
Hypergraph's agentless architecture delivers time-to-value in minutes, not months. Our pre-trained AI models begin detecting threats immediately, with continuous learning that adapts to your specific environment. No lengthy baseline periods required.
The Future of Agentless Security
Agentless network detection continues to evolve:
AI-Powered Analysis
Advanced machine learning, including Graph Neural Networks, enables detection of sophisticated attacks that rule-based systems miss. The network becomes a rich dataset for AI-driven threat hunting.
Encrypted Traffic Analysis
New techniques analyze encrypted traffic without decryption, using metadata, timing, and flow characteristics to detect threats inside TLS tunnels.
Cloud-Native Integration
As workloads move to cloud, agentless detection follows. VPC flow logs, cloud-native APIs, and traffic mirroring provide visibility without agents in cloud environments.
IT/OT Convergence
As IT and OT networks merge, unified agentless monitoring provides consistent visibility across both environments, essential for detecting attacks that pivot between them.
Protect What Agents Can't Reach
Hypergraph's agentless architecture provides complete visibility across IT, OT, and IoT environments. Protect your critical infrastructure without compromising operational integrity.
Request a DemoConclusion
Agentless network detection isn't just an alternative to endpoint security—it's an essential complement that provides visibility where agents cannot operate. For organizations with critical infrastructure, OT systems, medical devices, or legacy environments, it's often the only viable security option.
As networks grow more complex and attackers increasingly target operational technology, the ability to monitor without modifying becomes ever more valuable. The organizations that embrace agentless security today will be better positioned to protect the systems that matter most.
When you can't install agents, network visibility is your security lifeline.