They need both, but they solve different problems. Image scanning reduces known build-time risk, while runtime monitoring catches code that appears only after deployment. If the threat involves downloaded payloads, credential theft, or post-start behaviour, runtime monitoring is the control that actually sees the compromise.
Why image scanning alone does not answer the container security question
Image scanning is a build-time control. It helps catch known vulnerable packages, misconfigurations, and embedded secrets before deployment, which lowers the chance of shipping a predictable weakness. But it cannot see everything that happens after start-up, so it should be treated as one layer in a container security program, not the whole control set.
A scanner only evaluates what is present in the image at scan time. If a container downloads a second-stage payload, pulls attacker-controlled content, or later exposes credentials through process activity, the scan result may still look clean. That gap is why container security guidance treats image review and runtime visibility as complementary rather than interchangeable, as reflected in NIST SP 800-190 Container Security.
In practice, the biggest limitation is scope. Image scanning is strongest against known, static content; it is weaker against dynamic behaviour, inherited trust, and compromise that only appears after the workload is running. For teams trying to reduce pre-deployment risk, NHI Lifecycle Management Guide is useful reading because the same lifecycle discipline applies to container credentials, rotation, and visibility.
Why runtime monitoring matters when the threat is post-deployment
Runtime monitoring sees behaviour, not just contents. That makes it the control that can detect process injection, unexpected child processes, outbound connections, privilege escalation attempts, credential access, and lateral movement that occur after the container starts. If the compromise happens through downloaded code, a poisoned dependency, or an abused secret, runtime detection is often the first place the malicious activity becomes observable.
This is especially important for incidents that do not leave a clear image-level signature. A container can be built from a trusted image and still become dangerous later through shell access, remote code execution, or a stolen token. Runtime monitoring helps answer the operational question that image scanning cannot: what is this workload actually doing right now?
That distinction becomes concrete when secrets are present in images. NHIMG’s Massive Docker Hub Secrets Leak and Secrets in Docker Hub images both show why static checks matter, but also why post-start visibility still matters when stolen credentials are used after deployment.
How teams should combine both controls in a container security program
The practical answer is to use image scanning to reduce known build-time risk, then use runtime monitoring to detect what scanning could never prove: whether the running container stays within its expected behaviour. The two controls should be wired together so that a finding in one changes the handling of the other, for example blocking a risky image from promotion and flagging any workload that later behaves outside its approved process, network, or filesystem patterns.
Teams should also separate preventive and detective expectations. Image scanning is better for release gates, baseline hygiene, and compliance evidence. Runtime monitoring is better for containment, alerting, and investigation after deployment. If a team must choose only one for a temporary gap, runtime monitoring is usually the better choice for exposed or internet-facing workloads because it can reveal active compromise, not just known weaknesses.
Carbonato botnet 2026 is a good example of why this layered approach matters: once attackers get execution on a host or container, the relevant question becomes what they can do after start-up, not whether the original image looked clean.
Risk and Threat Considerations
Relying on image scanning alone creates blind spots for runtime-only compromise. Attackers can wait until execution, then fetch payloads, steal mounted secrets, or abuse environment credentials in ways that never appear in the image itself. The result is a false sense of coverage: the build pipeline looks controlled while the running workload remains exploitable.
Failure mechanism: Static inspection can confirm what was shipped, but it cannot confirm what the container downloads, executes, or exfiltrates after launch. If the runtime environment permits arbitrary network access or secret access, the attacker can pivot without changing the image.
Impact: Teams may miss active compromise, delayed credential theft, or post-deployment persistence, especially in fast-moving container estates where image immutability is assumed to equal workload safety.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-53 Rev 5 and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SI-4 — System Monitoring | Runtime container monitoring is continuous system-level detection of suspicious behavior. |
| CM-8 — System Component Inventory | Image scanning depends on knowing what images and components are deployed. | |
| RA-5 — Vulnerability Monitoring and Scanning | Image scanning is vulnerability and exposure discovery before deployment. | |
| Recommendation — Deploy SI-4 sensors and alerting for container runtime process, network, and file anomalies. Maintain CM-8 inventory of container images, tags, and deployed workloads before scanning and release. Use RA-5 to scan container images for known flaws and findings before promotion. | ||
| NIST CSF 2.0 | DE.CM-01 — Networks and network services are monitored to find anomalies | Container runtime monitoring detects anomalous execution and communication paths. |
| PR.DS-01 — Data-at-rest is protected | Image and runtime controls both protect secrets and sensitive data embedded in containers. | |
| Recommendation — Monitor container network and runtime behavior to detect deviations from expected service activity. Protect image layers, mounted secrets, and container data with strong encryption and access restrictions. | ||
Practitioner Guidance
What to prioritise: Treat image scanning as a release-quality control and runtime monitoring as an operational detection control. If the risk is known vulnerable software, scanner coverage matters first; if the risk is live exploitation, suspicious child processes, or secret abuse, runtime visibility matters first.
What to verify: Confirm that runtime policy can actually observe the behaviours you care about, including outbound connections, file writes, process spawning, and access to mounted secrets. If the monitoring only logs container start and stop events, it will not answer the security question the page is asking.
Practitioner takeaway: The right control is not “scan or monitor”, it is “scan to reduce what you ship, monitor to detect what the workload becomes.” Teams that collapse those two jobs into one usually discover the gap only after compromise.
Related resources from NHI Mgmt Group
- What breaks when security teams rely only on scanning and pre-runtime checks?
- What is the difference between image scanning and runtime drift prevention in container security?
- How should security teams investigate a compromised container when runtime activity points to the originating image and identity?
- What do security teams get wrong about container monitoring when they rely only on pre-production controls?