In this lesson, you will learn how to configure runtime security tools to detect and alert on suspicious system activity occurring inside your containerized environments.
While Kubernetes Audit logs (which we discussed in the previous section) monitor interactions with the API server, they do not see what happens inside the container’s kernel. To secure your workloads, you need deep visibility into system calls (syscalls) and file access patterns. Tools like Falco act as the industry standard here, leveraging eBPF or kernel modules to observe the behavior of your processes in real-time.
Capturing Anomalous Behavior
Runtime security tools work by defining a set of rules that trigger whenever a specific event occurs. You want to alert on patterns that deviate from normal operation, such as a shell being spawned in a production container, a binary being modified in /bin, or unexpected network connections.
Consider a simple rule configuration for detecting a sensitive file access attempt:
- rule: Detect sensitive file read
desc: Detects an attempt to read a sensitive system file
condition: >
evt.type = open and
container.id != host and
fd.name in (/etc/shadow, /etc/sudoers)
output: "Sensitive file read detected (user=%user.name file=%fd.name container=%container.id)"
priority: WARNING
From Detection to Response
When the tool detects an event matching that rule, it streams the alert to your security information and event management (SIEM) system or a logging pipeline. Because these tools hook into the kernel, they provide context that logs alone cannot, such as the exact process name, the user ID within the container, and the parent process that initiated the syscall.
By integrating these runtime alerts into your observability stack, you move beyond static vulnerability scanning. You are no longer just checking if an image is "clean" when it's built; you are actively monitoring it to ensure that even if a vulnerability is exploited, the resulting anomalous behavior—like writing to a read-only directory or spawning an unauthorized process—is caught and alerted on instantly.
Key Takeaway: Runtime security tools bridge the visibility gap between API-level auditing and internal process behavior, allowing you to detect and alert on malicious activity as it happens inside the container.