What Is Runtime Security? Protecting Applications at the Moment of Execution

Organizations invest heavily in pre-production security: SAST scans, software composition analysis, penetration testing. They add perimeter defences like WAFs and firewalls. And attacks still happen. They happen at runtime, in production, against live code that has already passed every pre-deployment check.

Runtime security is the protection layer that operates while software executes. It is not a replacement for what comes before it. It is the layer that covers what nothing else can reach.

There are two distinct types of runtime security, infrastructure and container-level, and application-level, and not every runtime solution covers both.

This is the hub article for Raven's runtime security cluster. It links out to related topics including runtime application self-protection, zero-day attack prevention, RASP vs WAF vs ADR, and vulnerability scanning.

Key Takeaways

• Runtime security protects software as it executes in production, not before deployment.
• It spans two layers: infrastructure and container security, and application-level runtime security. Not every runtime solution covers both.
• Application-level runtime security can block exploitation inside the running process, including zero-day attacks with no CVE, but this capability varies significantly by tool.
• Runtime security complements SAST, SCA, and WAF; it does not replace them.

What Is Runtime Security?

Runtime security is the set of technologies that protect software applications as they execute in production, detecting and blocking malicious behaviour at the moment it occurs rather than before deployment.

Two Layers of Runtime Security

Runtime security operates across two distinct layers, each covering a different part of the execution environment. Most tools address one layer. Some address both.

Layer 1: Infrastructure and container level. Secures the execution environment itself. Covers container escapes, privilege escalation, and malware present in container images. This layer monitors system calls and host behavior from outside the application process.

Layer 2: Application level. Secures what happens inside the running application code. Covers remote code execution attacks, zero-day exploits, and threats with no CVE. This layer monitors function calls, data flows, and execution context from within the process.

Not every runtime solution covers both layers. This article covers both but focuses primarily on application-level runtime security, where the most significant gap in traditional AppSec programs exists.

What Runtime Security Protects Against

Application-Level Threats

• Code injection attacks triggered in live execution — command injection and similar execution-time abuse — that bypass input validation at the moment the code runs.
• Zero-day exploits targeting unpatched or previously unknown vulnerabilities, where no pre-deployment scan would have detected the risk.
• CVE-less attacks: either a zero-day with no published identifier, or intended library behaviour that exposes risk in a specific application context — sometimes called a Shadow Vulnerability. Neither has a CVE. Neither can be caught by signature-based detection.
• Supply chain attacks: malicious code introduced before the SCA step, at the developer's machine or inside the CI pipeline, that is already present by the time any dependency scan runs.
• AI accelerates all of the above attack classes at a scale and speed that compress the window between discovery and active exploitation. It is not a separate threat category; it is a force multiplier on all of them.

Infrastructure and Container Threats

At the infrastructure level, runtime security addresses container escapes, privilege escalation, and malware hiding inside container images. These threats operate at the host and kernel level rather than inside the application process.

How Runtime Security Works

Infrastructure Runtime Security

Infrastructure runtime security monitors system calls, file access, and network connections originating from containers. It operates at the kernel level and uses predefined rules to identify deviations from expected behavior - detecting container escapes, privilege escalation, and unexpected process spawning.

Application Runtime Security

Application runtime security operates inside the running application process itself. It monitors function calls, data flows, and execution context in real time. When an attack is attempted, capable tools block it at the moment of exploitation rather than alerting after the fact, though not all application runtime tools offer prevention; some are detection-only.

Runtime Security in Kubernetes

Kubernetes provides RBAC, network policies, and pod security standards, but these are access and perimeter controls, not application runtime protection. They govern who can do what, not what the running application code itself is doing.

Container-Level Tools

Container runtime security tools deploy as a DaemonSet, placing one agent per node. They use predefined rules to identify deviations at the container and node level, watching for anomalous system calls, unexpected process spawning, and suspicious file access.

Application-Level Tools

Application runtime security monitors execution inside the application directly. Deployment models vary: some vendors require code changes or library instrumentation; others attach at the kernel level without modifying the application. Prevention capability also varies - some tools detect and alert, others can block at the moment of exploitation.

Raven deploys as a DaemonSet via a single Helm command across EKS, GKE, and AKS. It requires no code changes and no pod restarts, and blocks attacks at the moment of execution. Learn more about runtime application prevention.

Runtime Security vs Pre-Production Security

Pre-production scanning is essential. It is also insufficient on its own.

SAST finds first-party code issues before deployment and improves code posture. It cannot observe or respond to behavior that only emerges during live execution.

SCA identifies known CVEs in open source dependencies and improves dependency posture. It cannot tell which vulnerable functions are actually called at runtime. For more on this gap, see software composition analysis.

‍Vulnerability scanning identifies known weaknesses across infrastructure and dependencies. It is blind to zero-day attacks and novel exploits. See vulnerability scanning for a full breakdown.

All three improve security posture before deployment. Runtime security protects the running application while it executes.

Types of Runtime Security Tools

Container runtime security monitors system calls and container behaviour at the host level. These tools operate via kernel-level rules, watching what containers do on the underlying host and alerting when behaviour deviates from defined policy.

RASP (Runtime Application Self-Protection) embeds in the application runtime and monitors function execution from within the running process. It can block attacks at the point of exploitation because it operates inside the application rather than watching it from outside. For a full comparison with perimeter tooling, see runtime application self-protection.

ADR (Application Detection and Response) provides application-level detection and investigation context, connecting runtime events back to the specific library, function, and call chain responsible. It adds depth to what RASP-style prevention sees, giving security teams root cause rather than just a blocked event.

EDR and XDR provide endpoint detection and response. They detect host-level anomalies and are strong at identifying malware and lateral movement, but they have limited application-layer visibility and typically cannot block injection attacks or zero-day exploits inside a running process.

Runtime SCA monitors which vulnerable open source functions are actually called in live execution. Rather than flagging every dependency with a matching CVE, runtime SCA surfaces only the findings where the vulnerable function is executing. Runtime SCA, ADR detection, and runtime prevention work together: SCA identifies what is exposed, ADR shows the context, and prevention blocks the exploit.

FAQs

What is runtime security in cybersecurity? Runtime security is the set of technologies that protect software applications while they are executing in production. It detects and responds to malicious behavior in real time, covering threats that pre-production scanning and perimeter defences cannot reach.

What is the difference between runtime security and static security? Static security tools such as SAST and SCA analyse code and dependencies before deployment and improve security posture. They cannot observe or respond to behaviour that only emerges during live execution. Runtime security operates in production and protects the running application directly.

What is Kubernetes runtime security? Kubernetes runtime security refers to tools and practices that protect workloads running inside a Kubernetes cluster. It spans container-level monitoring and application-level protection, covering threats that Kubernetes-native controls like RBAC and network policies do not address.

What tools provide runtime security? The main categories are container runtime security tools, RASP (runtime application self-protection), ADR (application detection and response), EDR/XDR platforms, and runtime SCA tools. Each operates at a different layer, and most production AppSec programmes combine more than one.

What is eBPF-based runtime security? eBPF (Extended Berkeley Packet Filter) is a kernel-level technology that allows programs to run safely inside the Linux kernel without modifying kernel source code. eBPF is used as a deployment mechanism by several runtime security tools. Specific capabilities, such as whether code changes are required, performance overhead, and whether the tool can prevent attacks or only detect them, vary by implementation.

Is RASP the same as runtime security? RASP is one category of runtime security, specifically the application-level layer that embeds inside the running process. Runtime security is the broader discipline, encompassing container security, infrastructure monitoring, RASP, ADR, runtime SCA, and EDR tools.

What threats does runtime security protect against? Runtime security covers code injection attacks, zero-day exploits, CVE-less threats, supply chain attacks that activate at runtime, container escapes, and privilege escalation. Coverage depends on which layer and which tool, not every runtime security product addresses every category.

How does runtime security handle zero-day attacks? Application-level runtime security tools that detect based on behavior, rather than known CVE signatures, can block zero-day exploits at the moment of execution. This is not a universal property of all runtime tools; it applies specifically to tools with behavioral detection and prevention capability at the application layer.

Conclusion

Runtime security is the production protection layer that pre-production scanning and perimeter tools cannot replace. Pre-production tools improve posture. Runtime security protects the application while it runs — including against zero-days, CVE-less threats, and known CVEs.

‍See how Raven protects runtime execution across your workloads, detecting and blocking attacks at the application layer without requiring code changes.