Detection rules › Panther
Kubernetes API Multiple 403 Responses from Single Public IP
This detection identifies when a public source IP generates multiple 403 (Forbidden) responses from the Kubernetes API server. This pattern may indicate reconnaissance attempts, permission enumeration, brute force attacks, or misconfigured access. Private IPs are excluded as they typically represent legitimate internal traffic.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Discovery | T1613 Container and Resource Discovery |
Rule body yaml
AnalysisType: rule
Filename: k8s_multiple_403_public_ip.py
RuleID: "Kubernetes.API.Multiple403.PublicIP"
DisplayName: "Kubernetes API Multiple 403 Responses from Single Public IP"
Enabled: true
Status: Experimental
LogTypes:
- Amazon.EKS.Audit
- Azure.MonitorActivity
- GCP.AuditLog
Tags:
- Kubernetes
- Security Control
- Container and Resource Discovery
- Unified Detection
Reports:
MITRE ATT&CK:
- TA0007:T1613 # Container and Resource Discovery
Reference: https://aws.github.io/aws-eks-best-practices/security/docs/detective/
Severity: Info
Description: >
This detection identifies when a public source IP generates multiple 403 (Forbidden)
responses from the Kubernetes API server. This pattern may indicate reconnaissance
attempts, permission enumeration, brute force attacks, or misconfigured access.
Private IPs are excluded as they typically represent legitimate internal traffic.
Runbook: |
1. Find all API requests from the sourceIPs address in the 1 hour before and after the alert to identify attempted operations
2. Identify which API resources or operations the source IP attempted to access to determine if this is systematic probing or random scanning
3. Check if the same source IP has generated 403 errors against other Kubernetes clusters in the past 24 hours to assess campaign scope
DedupPeriodMinutes: 30
Threshold: 10
SummaryAttributes:
- username
- p_any_ip_addresses
- p_source_label
Tests:
- Name: EKS 403 from Public IP
ExpectedResult: true
Log:
{
"kind": "Event",
"apiVersion": "audit.k8s.io/v1",
"auditID": "abc-123",
"verb": "watch",
"user": {"username": "system:serviceaccount:kube-system:coredns"},
"sourceIPs": ["5.5.5.5"],
"objectRef": {
"apiGroup": "discovery.k8s.io",
"apiVersion": "v1",
"resource": "endpointslices"
},
"responseStatus": {"code": 403},
"stage": "ResponseComplete",
"userAgent": "Go-http-client/2.0",
"p_log_type": "Amazon.EKS.Audit",
"p_source_label": "eks-cluster",
"p_any_ip_addresses": ["5.5.5.5"]
}
- Name: AKS 403 from Public IP
ExpectedResult: true
Log:
{
"p_log_type": "Azure.MonitorActivity",
"category": "kube-audit",
"operationName": "Microsoft.ContainerService/managedClusters/diagnosticLogs/Read",
"properties": {
"log": "{\"kind\":\"Event\",\"apiVersion\":\"audit.k8s.io/v1\",\"verb\":\"get\",\"user\":{\"username\":\"test-user\"},\"sourceIPs\":[\"8.8.8.8\"],\"objectRef\":{\"resource\":\"pods\",\"namespace\":\"default\"},\"responseStatus\":{\"code\":403},\"stage\":\"ResponseComplete\"}"
},
"p_source_label": "aks-cluster",
"p_any_ip_addresses": ["8.8.8.8"]
}
- Name: GCP GKE 403 from Public IP
ExpectedResult: true
Log:
{
"protoPayload": {
"authenticationInfo": {"principalEmail": "user@example.com"},
"methodName": "io.k8s.core.v1.pods.list",
"requestMetadata": {
"callerIP": "1.2.3.4",
"callerSuppliedUserAgent": "kubectl/v1.27.0"
},
"resourceName": "core/v1/namespaces/default/pods",
"serviceName": "k8s.io",
"status": {"code": 7, "message": "Forbidden"}
},
"resource": {
"type": "k8s_cluster",
"labels": {"project_id": "test-project"}
},
"p_log_type": "GCP.AuditLog",
"p_source_label": "gke-cluster",
"p_any_ip_addresses": ["1.2.3.4"]
}
- Name: 403 from Private IP (Excluded)
ExpectedResult: false
Log:
{
"kind": "Event",
"verb": "watch",
"user": {"username": "system:serviceaccount:kube-system:coredns"},
"sourceIPs": ["10.0.27.115"],
"responseStatus": {"code": 403},
"p_log_type": "Amazon.EKS.Audit"
}
- Name: 200 Response (Not 403)
ExpectedResult: false
Log:
{
"kind": "Event",
"verb": "get",
"sourceIPs": ["5.5.5.5"],
"responseStatus": {"code": 200},
"p_log_type": "Amazon.EKS.Audit"
}
- Name: No Source IP
ExpectedResult: false
Log:
{
"kind": "Event",
"verb": "get",
"sourceIPs": [],
"responseStatus": {"code": 403},
"p_log_type": "Amazon.EKS.Audit"
}
Detection logic
Condition
responseStatus.code in ["403", "7"]
sourceIPs is_not_null
This rule also runs imperative logic the parser cannot express as a filter; the conditions above are the structured part it could extract.
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
responseStatus.code | in |
|
sourceIPs | is_not_null |
Output fields
Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.
| Field | Source |
|---|---|
username | |
sourceIPs | |
userAgent | |
namespace | |
verb | |
resource | |
requestURI | |
responseStatus | |
cluster | p_source_label |