Elastic medium stable kql

Kubernetes Secret or ConfigMap Access via Azure Arc Proxy

Detects when secrets or configmaps are accessed, created, modified, or deleted in a Kubernetes cluster by the Azure Arc AAD proxy service account. When operations are routed through the Azure Arc Cluster Connect proxy, the Kubernetes audit log records the acting user as system:serviceaccount:azure-arc:azure-arc-kube-aad-proxy-sa with the actual caller identity in the impersonatedUser field. This pattern indicates that someone is accessing the cluster through the Azure ARM API rather than directly via kubectl against the API server. While legitimate for Arc-managed workflows, adversaries with stolen service principal credentials can abuse Arc Cluster Connect to read, exfiltrate, or modify secrets and configmaps while appearing as the Arc proxy service account in K8s audit logs. This rule uses a 5-day new-terms history window keyed on the impersonated identity and alerts the first time that Azure AD principal performs this activity.

View Source

Detection Logic

FROM logs-kubernetes.audit_logs-* metadata _id, _version, _index
| WHERE STARTS_WITH(kubernetes.audit.user.username, "system:serviceaccount:azure-arc:")
    
AND kubernetes.audit.objectRef.resource IN ("secrets", "configmaps")
    
AND kubernetes.audit.verb IN ("get", "list", "create", "update", "patch", "delete")
    
AND kubernetes.audit.objectRef.namespace NOT IN ("azure-arc", "azure-arc-release", "kube-system")
    
AND NOT STARTS_WITH(kubernetes.audit.objectRef.name, "sh.helm.release.v1")
| STATS
    Esql.verb_values = VALUES(kubernetes.audit.verb),
    Esql.resource_type_values = VALUES(kubernetes.audit.objectRef.resource),
    Esql.resource_name_values = VALUES(kubernetes.audit.objectRef.name),
    Esql.namespace_values = VALUES(kubernetes.audit.objectRef.namespace),
    Esql.data_stream_namespace_values = VALUES(data_stream.namespace),
    Esql.acting_user_values = VALUES(kubernetes.audit.user.username),
    Esql.user_agent_values = VALUES(kubernetes.audit.userAgent),
    Esql.source_ips_values = VALUES(kubernetes.audit.sourceIPs),
    Esql.response_code_values = VALUES(kubernetes.audit.responseStatus.code),
    Esql.timestamp_first_seen = MIN(@timestamp),
    Esql.timestamp_last_seen = MAX(@timestamp),
    Esql.event_count = COUNT(*)
    BY kubernetes.audit.impersonatedUser.username
| WHERE Esql.timestamp_first_seen >= NOW() - 9 minutes
| KEEP kubernetes.audit.impersonatedUser.username, Esql.*

False Positives

  • ⚠ Azure Arc system components may create or update secrets and configmaps in the azure-arc and azure-arc-release namespaces during normal cluster management. Filter by namespace to exclude these.
  • ⚠ Helm operations managed through Arc may create release secrets (prefixed with sh.helm.release.v1). These are normal Arc lifecycle operations.

Field Validations

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