Keep agentless scanning for broad inventory and exposure management, but add continuous runtime detection when workloads are live, privileged, or subject to active exploitation risk. If your main question is what is running versus what is happening right now, you need both lenses.
Why agentless scanning alone is not enough once workloads are live
agentless scanning is strongest when you need breadth: fast inventory, exposure mapping, and a low-friction way to see what exists across many assets. Its blind spot is time. A snapshot can tell you that a workload is present and that a weakness exists, but it cannot reliably tell you whether that weakness is being exercised right now, whether a privileged process has changed behaviour, or whether an attacker has already moved from exposure to exploitation.
That is why the decision point is not “agentless or runtime”, but “what kind of answer do we need”. If you are still discovering assets, chasing drift, or building baseline exposure management, scanning can do most of the work. Once workloads are production-critical, high-privilege, or exposed to active threat activity, continuous runtime detection becomes the complementary control because it observes actual execution, not just configuration or image state.
For teams that manage large estates, agentless discovery remains useful as a control-plane view, while runtime detection gives the data-plane view. A common mistake is to assume one view can substitute for the other. It cannot, especially when the question shifts from hygiene to compromise detection, containment, or response.
When the workload’s operating state changes the control choice
The need for runtime detection rises when the workload can materially affect the environment while it is running. That includes production systems with privileged access, workloads that handle sensitive data, internet-facing services, and components that often become attacker pivots after initial access. In those cases, the relevant security question is not only whether the workload is configured safely, but whether it is behaving safely under live conditions.
Runtime detection is also the better fit when you care about short-lived abuse, command execution, suspicious network paths, process injection, unexpected child processes, or file and registry changes that never appear in a scan result. MITRE D3FEND is useful here because it frames defensive observation and response as distinct from static assessment, which matches the practical split between exposure management and live detection.
In containerised and orchestrated environments, the case for runtime detection is even stronger because the runtime surface can change faster than image or inventory data. NIST SP 800-190 Container Security is a helpful reference because it distinguishes image, registry, orchestrator, and runtime concerns. The same principle applies outside containers: the more ephemeral the workload, the less complete static visibility becomes on its own.
Agentless scanning should still stay in place, but it should be treated as the upstream view that tells you where to look more closely, not as the final verdict on current compromise state.
How to decide on both lenses in practice
The most reliable decision rule is simple: keep agentless scanning for coverage, and add continuous runtime detection when the workload’s failure mode includes active abuse, privilege escalation, lateral movement, or fast-changing execution. If the asset is disposable and low impact, scanning may be enough. If the asset is durable, privileged, or a likely target, runtime detection becomes part of the minimum viable control set.
For live services, the strongest pairing is broad discovery plus behaviour-sensitive monitoring. Agentless scanning helps answer what exists, what is missing, and what is exposed. Runtime detection helps answer what changed, what executed, and what deserves immediate response. That combination is especially important when teams need to distinguish stale exposure from active exploitation risk.
SANS Security Resources is a practical place to anchor the operational side of this choice because detection engineering and incident handling depend on live signals, not just asset snapshots. For teams formalising the control model, NIST Cybersecurity Framework 2.0 is a useful umbrella because it separates identify and protect activities from detect and respond activities, which mirrors the split between scanning and runtime telemetry.
Where the workload is privileged, internet-exposed, or tied to critical business services, runtime detection should not be optional. Where the workload is numerous but low risk, agentless scanning may remain the primary control, with runtime detection reserved for the most consequential subset.
Risk and Threat Considerations
Agentless scanning creates blind spots when defenders assume a point-in-time view is enough to catch live compromise. The risk is highest in workloads that can be abused quickly, because attackers often care less about how the system is configured in a scan and more about what they can do before the next assessment cycle.
Failure mechanism: Static visibility misses malicious execution, privilege abuse, transient persistence, and fast-moving lateral activity, so an attacker can operate between scans or without changing the observable configuration state.
Impact: Teams may underestimate exposure, delay containment, and miss the earliest signs of exploitation on workloads that matter most, especially where privileged services or production systems are involved.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 addresses the attack and risk surface, while NIST SP 800-53 Rev 5, NIST CSF 2.0 and CIS Controls v8 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SI-4 — System Monitoring | Continuous runtime detection is a direct monitoring control for live workload behavior. |
| CA-7 — Continuous Monitoring | The question is about when continuous runtime detection should supplement periodic scanning. | |
| RA-5 — Vulnerability Monitoring and Scanning | Agentless scanning supports broad exposure discovery and vulnerability visibility. | |
| Recommendation — Deploy SI-4 monitoring on live workloads to detect malicious behavior and trigger response. Use CA-7 to combine periodic exposure scanning with continuous telemetry for higher-risk workloads. Use RA-5 for estate-wide scanning and exposure tracking, then escalate to runtime detection where needed. | ||
| NIST CSF 2.0 | DE.CM-01 — Networks and devices are monitored to find events | Runtime detection is about monitoring live events beyond static inventory. |
| ID.AM-01 — Physical devices and systems within the organization are inventoried | Agentless scanning supports broad inventory and exposure management. | |
| Recommendation — Extend monitoring to live workload events so active exploitation is detected sooner. Maintain inventory through agentless discovery, then layer runtime detection on critical assets. | ||
| CIS Controls v8 | CIS-13 — Network Monitoring and Defense | Runtime detection depends on observing live activity and suspicious behavior. |
| CIS-7 — Continuous Vulnerability Management | Agentless scanning fits continuous exposure and vulnerability management. | |
| Recommendation — Add live monitoring for workloads that need behavioral detection beyond static scans. Run continuous scanning for coverage, and add runtime telemetry for high-risk production workloads. | ||
| OWASP Non-Human Identity Top 10 | NHI-02 — Secret Leakage | Live detection matters when runtime compromise can expose or abuse secrets. |
| NHI-05 — Overprivileged NHI | Runtime detection is important when privileged workloads may be abused after deployment. | |
| Recommendation — Monitor workloads that can leak or misuse secrets during execution, not just at rest. Prioritise runtime detection on overprivileged workloads where live abuse would be high impact. | ||
Practitioner Guidance
What to prioritise: Keep agentless scanning as the estate-wide baseline, then prioritise runtime detection for any workload that can materially expand blast radius if compromised. The trigger is not the tool category, it is the consequence of missed live activity.
What to verify: Confirm that the workload class you are exempting from runtime monitoring is genuinely low impact, low privilege, and not a bridge to sensitive systems. If it can be used for privilege escalation, credential access, or lateral movement, treat runtime telemetry as mandatory.
What good looks like: Scanning tells you what is present and exposed, runtime detection tells you when behaviour changes in ways that warrant triage. The mature state is not replacing one with the other, but using each where its visibility is strongest.
Practitioner takeaway: Use agentless scanning for breadth and runtime detection for truth under live conditions, especially where privileged or production workloads turn exposure into immediate security risk.
Related resources from NHI Mgmt Group
- How can security teams decide whether to add continuous exposure scanning before expanding pentest frequency?
- How should cloud security teams balance agentless scanning with agent-based runtime protection?
- Should teams prioritise runtime controls over more vulnerability scanning?
- How should security teams combine agentless and agent-based Kubernetes scanning?