Implementing Runtime Security Monitoring

Implementing Runtime Security Monitoring

Runtime security monitoring detects anomalous behaviors that may indicate compromises or attacks. Unlike static security controls, runtime monitoring observes actual container behavior, detecting zero-day exploits and insider threats. Effective monitoring requires understanding normal application behavior to distinguish legitimate activities from potential threats.

System call monitoring forms the foundation of runtime security. Abnormal system call patterns often indicate exploitation attempts or malicious activities. Tools like Falco, Sysdig Secure, and Aqua Security monitor system calls in real-time, alerting on suspicious activities. These tools use rule engines to define expected behaviors and detect deviations.

# Falco rules for runtime security monitoring
- rule: Container Shell Spawned
  desc: Detect shell spawned in a container
  condition: >
    container.id != host and
    proc.name in (shell_binaries) and
    spawned_process and
    not container.image.repository in (allowed_shell_containers)
  output: >
    Shell spawned in container (user=%user.name container=%container.name 
    shell=%proc.name parent=%proc.pname cmdline=%proc.cmdline)
  priority: WARNING
  tags: [container, shell, mitre_execution]

- rule: Write below etc
  desc: Detect writes to /etc directory
  condition: >
    container.id != host and
    write and
    fd.name startswith /etc/ and
    not proc.name in (package_mgmt_binaries) and
    not container.image.repository in (allowed_etc_writers)
  output: >
    File written under /etc (user=%user.name command=%proc.cmdline 
    file=%fd.name container=%container.name)
  priority: ERROR
  tags: [container, filesystem, mitre_persistence]

- rule: Outbound Connection to C2 Servers
  desc: Detect outbound connections to known C2 servers
  condition: >
    container.id != host and
    outbound and
    fd.sip in (c2_server_ips) and
    not proc.name in (allowed_outbound_procs)
  output: >
    Outbound connection to C2 server (command=%proc.cmdline 
    connection=%fd.name container=%container.name)
  priority: CRITICAL
  tags: [network, c2, mitre_command_and_control]

- rule: Container Privilege Escalation
  desc: Detect privilege escalation attempts
  condition: >
    container.id != host and
    proc.name in (su, sudo, setuid_binaries) and
    not container.image.repository in (allowed_privilege_escalation)
  output: >
    Privilege escalation attempt (user=%user.name command=%proc.cmdline 
    container=%container.name)
  priority: CRITICAL
  tags: [container, privilege_escalation, mitre_privilege_escalation]

File integrity monitoring complements system call monitoring by detecting unauthorized file modifications. Runtime security tools can monitor critical directories and alert on changes. This capability proves particularly valuable for detecting web shells, backdoors, and configuration tampering. Integration with admission controllers can prevent deployment of containers with modified files.