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[New/Tuning] Direct Kubelet API Access rules (#5996)

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* [New/Tuning] Direct Kubelet API Access rules

- tuned existing rule for D4C to bump-up severity to high (low FP and very susp behavior) + added 10255 port and wss url.
- duplicated same rule logic for auditd/endpoint compatibility for both 10250 port in args and kubeletctl exec.
- added a new one using network event vs process argument for more resilience.

* ++

* Update discovery_potential_direct_kubelet_access_via_process_args.toml

* Update and rename discovery_potential_direct_kubelet_access_via_process_args.toml to lateral_movement_direct_kubelet_access_via_process_args.toml

* Update rules/linux/lateral_movement_direct_kubelet_access_via_process_args.toml

Co-authored-by: Isai <59296946+imays11@users.noreply.github.com>

* Update rules/linux/discovery_potential_kubeletctl_execution.toml

Co-authored-by: Isai <59296946+imays11@users.noreply.github.com>

* Update discovery_potential_kubeletctl_execution.toml

* Update lateral_movement_kubelet_api_connection_attempt_internal_ip.toml

* Apply suggestion from @Aegrah

Co-authored-by: Ruben Groenewoud <78494512+Aegrah@users.noreply.github.com>

* Apply suggestion from @Aegrah

Co-authored-by: Ruben Groenewoud <78494512+Aegrah@users.noreply.github.com>

---------

Co-authored-by: Isai <59296946+imays11@users.noreply.github.com>
Co-authored-by: Ruben Groenewoud <78494512+Aegrah@users.noreply.github.com>
This commit is contained in:
Samirbous
2026-05-04 22:18:23 +01:00
committed by GitHub
parent 0b15511ef5
commit 83406d8ce1
5 changed files with 408 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files
rules/integrations/cloud_defend/execution_kubeletctl_execution.toml
+3 -3
View File
@@ -4,7 +4,7 @@ integration = ["cloud_defend"]
maturity = "production"
min_stack_comments = "Defend for Containers integration was re-introduced in 9.3.0"
min_stack_version = "9.3.0"
updated_date = "2026/03/24"
updated_date = "2026/04/28"
[rule]
author = ["Elastic"]
@@ -62,9 +62,9 @@ references = [
"https://www.cyberark.com/resources/threat-research-blog/using-kubelet-client-to-attack-the-kubernetes-cluster",
"https://github.com/cyberark/kubeletctl",
]
risk_score = 21
risk_score = 73
rule_id = "2572f7e0-7647-4c68-a42b-d3b1973deaae"
severity = "low"
severity = "high"
tags = [
"Data Source: Elastic Defend for Containers",
"Domain: Container",
rules/integrations/cloud_defend/execution_potential_direct_kubelet_access_via_process_args.toml
+4 -4
View File
@@ -4,7 +4,7 @@ integration = ["cloud_defend"]
maturity = "production"
min_stack_comments = "Defend for Containers integration was re-introduced in 9.3.0"
min_stack_version = "9.3.0"
updated_date = "2026/03/24"
updated_date = "2026/04/28"
[rule]
author = ["Elastic"]
@@ -56,9 +56,9 @@ references = [
"https://www.cyberark.com/resources/threat-research-blog/using-kubelet-client-to-attack-the-kubernetes-cluster",
"https://www.aquasec.com/blog/kubernetes-exposed-exploiting-the-kubelet-api/"
]
risk_score = 47
risk_score = 73
rule_id = "b4bd186b-69c6-45ad-8bef-5c35bbadeaef"
severity = "medium"
severity = "high"
tags = [
"Data Source: Elastic Defend for Containers",
"Domain: Container",
@@ -72,7 +72,7 @@ timestamp_override = "event.ingested"
type = "eql"
query = '''
process where host.os.type == "linux" and event.type == "start" and event.action == "exec" and
process.args like "http*:10250*" and process.interactive == true and container.id like "?*"
process.args like ("http*:10250*", "http*:10255*", "wss:*:10250*", "wss:*:10255*") and container.id like "?*"
'''
[[rule.threat]]
rules/linux/discovery_potential_kubeletctl_execution.toml
+120
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@@ -0,0 +1,120 @@
[metadata]
creation_date = "2026/04/28"
integration = ["endpoint", "auditd_manager"]
maturity = "production"
updated_date = "2026/04/28"
[rule]
author = ["Elastic"]
description = """
Detects the execution of kubeletctl on Linux hosts. Kubeletctl is a command-line tool that can be used to interact with
the Kubelet API directly, simplifying access to Kubelet endpoints that can be used for discovery and, in some cases,
lateral movement within Kubernetes environments.
"""
false_positives = [
"""
Administrators or developers may execute kubeletctl during legitimate troubleshooting or incident response to validate
Kubelet API connectivity or enumerate pods. Confirm the user/session and change window before escalating.
""",
]
from = "now-9m"
index = ["auditbeat-*", "logs-auditd_manager.auditd-*", "logs-endpoint.events.process*"]
language = "eql"
license = "Elastic License v2"
name = "Potential Kubeletctl Execution"
note = """## Triage and analysis
> **Disclaimer**:
> This investigation guide was created using generative AI technology and has been reviewed to improve its accuracy and relevance. While every effort has been made to ensure its quality, we recommend validating the content and adapting it to suit your specific environment and operational needs.
### Investigating Potential Kubeletctl Execution
This alert flags kubeletctl execution on a Linux host. Kubeletctl provides direct access to the node’s Kubelet API and can
be used to enumerate pods and nodes and attempt actions such as exec/attach/portForward. A common attacker pattern is
running `kubeletctl scan` to find reachable Kubelet endpoints, then using `pods` or `exec/attach` for follow-on access.
### Possible investigation steps
- Review the full command line to identify the intended operation (scan/pods/exec/attach/portForward) and the target
Kubelet endpoint (node IP/hostname and port via `-s`/`--server`).
- Correlate with host and container telemetry for connections to Kubelet ports (commonly 10250/10255) and look for
scanning patterns across multiple nodes.
- Check whether Kubernetes credentials were accessed or used (service account tokens, kubeconfigs, client certs) and
correlate with Kubernetes audit logs for follow-on actions.
### False positive analysis
- Approved operational debugging or incident response activity that uses kubeletctl for diagnostics.
### Response and remediation
- Restrict access to Kubelet ports at the network layer and harden Kubelet authentication/authorization.
- Rotate/revoke any exposed Kubernetes credentials and investigate for follow-on discovery or execution attempts.
"""
references = [
"https://www.cyberark.com/resources/threat-research-blog/using-kubelet-client-to-attack-the-kubernetes-cluster",
"https://github.com/cyberark/kubeletctl",
]
risk_score = 47
rule_id = "f7a131f8-44b7-4957-99a4-e6c54d93d816"
severity = "medium"
tags = [
"Domain: Endpoint",
"Domain: Container",
"Domain: Kubernetes",
"OS: Linux",
"Use Case: Threat Detection",
"Tactic: Execution",
"Tactic: Discovery",
"Data Source: Elastic Defend",
"Data Source: Auditd Manager",
"Resources: Investigation Guide",
]
timestamp_override = "event.ingested"
type = "eql"
query = '''
process where host.os.type == "linux" and event.type == "start" and event.action in ("exec", "executed") and
(
process.name == "kubeletctl" or
(process.args in ("run", "exec", "scan", "pods", "runningpods", "attach", "portForward", "cri", "pid2pod") and process.args:("*:10250*", "*:10255*"))
)
'''
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1613"
name = "Container and Resource Discovery"
reference = "https://attack.mitre.org/techniques/T1613/"
[rule.threat.tactic]
id = "TA0007"
name = "Discovery"
reference = "https://attack.mitre.org/tactics/TA0007/"
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1059"
name = "Command and Scripting Interpreter"
reference = "https://attack.mitre.org/techniques/T1059/"
[[rule.threat.technique.subtechnique]]
id = "T1059.004"
name = "Unix Shell"
reference = "https://attack.mitre.org/techniques/T1059/004/"
[[rule.threat.technique]]
id = "T1609"
name = "Container Administration Command"
reference = "https://attack.mitre.org/techniques/T1609/"
[rule.threat.tactic]
id = "TA0002"
name = "Execution"
reference = "https://attack.mitre.org/tactics/TA0002/"
rules/linux/lateral_movement_direct_kubelet_access_via_process_args.toml
+136
View File
@@ -0,0 +1,136 @@
[metadata]
creation_date = "2026/04/28"
integration = ["endpoint", "auditd_manager"]
maturity = "production"
updated_date = "2026/04/28"
[rule]
author = ["Elastic"]
description = """
Detects potential direct Kubelet API access attempts on Linux by identifying process executions whose arguments contain
URLs targeting Kubelet ports (10250/10255). Adversaries may probe or access Kubelet endpoints to enumerate pods, fetch
logs, or attempt remote execution, which can enable discovery and lateral movement in Kubernetes environments.
"""
false_positives = [
"""
Cluster operators and node diagnostics may legitimately probe Kubelet endpoints (for example /pods or /metrics) during
troubleshooting. Validate the initiating user, session, and whether the target node/IP is expected for the host.
""",
]
from = "now-9m"
index = ["auditbeat-*", "logs-auditd_manager.auditd-*", "logs-endpoint.events.process*"]
language = "eql"
license = "Elastic License v2"
name = "Potential Direct Kubelet Access via Process Arguments"
note = """## Triage and analysis
> **Disclaimer**:
> This investigation guide was created using generative AI technology and has been reviewed to improve its accuracy and relevance. While every effort has been made to ensure its quality, we recommend validating the content and adapting it to suit your specific environment and operational needs.
### Investigating Potential Direct Kubelet Access via Process Arguments
This detection flags a process on a Linux host whose arguments include a URL targeting the Kubelet API ports 10250/10255.
Attackers often use `curl`, `wget`, or scripting runtimes to access endpoints such as `/pods`, `/runningpods`,
`/metrics`, `/exec`, or `/containerLogs`. Successful access can provide node and workload visibility, and in some cases
enable actions that facilitate lateral movement within the cluster.
### Possible investigation steps
- Extract and reconstruct the full URL from `process.args` / `process.command_line`, including the hostname/IP, port, and
path, and determine whether the request intent was discovery or execution.
- Identify the user and session that launched the process and whether it originated from an interactive shell, scheduled
task, or automation.
- Correlate the timestamp with Kubernetes audit logs and node/Kubelet logs to confirm whether the request was
authenticated and whether it returned success.
- If the destination is a node IP, check whether this host should be allowed to reach node Kubelet ports and whether
other nodes were contacted in a scanning pattern.
### False positive analysis
- SRE/operator troubleshooting sessions validating Kubelet reachability or TLS/auth behavior.
- Approved health checks, debugging scripts, or node agents that query Kubelet endpoints.
### Response and remediation
- Restrict access to Kubelet ports 10250/10255 at the network layer; block pod-to-node or host-to-node traffic except for
approved agents.
- Rotate any potentially exposed credentials (service account tokens, client certs, kubeconfigs) and assess for follow-on
activity such as `exec/attach` and secret reads.
- Harden Kubelet configuration (disable anonymous auth, enforce webhook authn/authz) and review RBAC/admission controls.
"""
references = [
"https://heilancoos.github.io/research/2025/12/16/kubernetes.html#kubelet-api",
"https://www.cyberark.com/resources/threat-research-blog/using-kubelet-client-to-attack-the-kubernetes-cluster",
"https://www.aquasec.com/blog/kubernetes-exposed-exploiting-the-kubelet-api/",
]
risk_score = 73
rule_id = "6aa52f86-18f1-4a5a-a0ac-e2b5db8af589"
severity = "high"
tags = [
"Domain: Endpoint",
"Domain: Container",
"Domain: Kubernetes",
"OS: Linux",
"Use Case: Threat Detection",
"Tactic: Discovery",
"Tactic: Lateral Movement",
"Data Source: Elastic Defend",
"Data Source: Auditd Manager",
"Resources: Investigation Guide",
]
timestamp_override = "event.ingested"
type = "eql"
query = '''
process where host.os.type == "linux" and event.type == "start" and event.action in ("exec", "executed") and
(
/* direct utility execution */
process.name like ("curl", "wget", "python*", "perl*", "php*", "node*", "java", "ruby*", "lua*", ".*") or
process.executable like ("/tmp/*", "/var/tmp/*", "/dev/shm/*", "/var/run/*", "/home/*", "/run/user/*", "/busybox/*")
) and
process.args like ("http*:10250/*", "http*:10255/*", "wss:*:10250/*", "wss:*:10255/*")
'''
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1021"
name = "Remote Services"
reference = "https://attack.mitre.org/techniques/T1021/"
[rule.threat.tactic]
id = "TA0008"
name = "Lateral Movement"
reference = "https://attack.mitre.org/tactics/TA0008/"
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1613"
name = "Container and Resource Discovery"
reference = "https://attack.mitre.org/techniques/T1613/"
[rule.threat.tactic]
id = "TA0007"
name = "Discovery"
reference = "https://attack.mitre.org/tactics/TA0007/"
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1059"
name = "Command and Scripting Interpreter"
reference = "https://attack.mitre.org/techniques/T1059/"
[[rule.threat.technique.subtechnique]]
id = "T1059.004"
name = "Unix Shell"
reference = "https://attack.mitre.org/techniques/T1059/004/"
[rule.threat.tactic]
id = "TA0002"
name = "Execution"
reference = "https://attack.mitre.org/tactics/TA0002/"
rules/linux/lateral_movement_kubelet_api_connection_attempt_internal_ip.toml
+145
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@@ -0,0 +1,145 @@
[metadata]
creation_date = "2026/04/28"
integration = ["endpoint", "auditd_manager"]
maturity = "production"
updated_date = "2026/04/28"
[rule]
author = ["Elastic"]
description = """
Detects network connection attempts to the Kubernetes Kubelet API port (10250/10255) on internal IP ranges from Linux hosts.
This rule focuses on common request and scripting utilities (curl, wget, python, node, etc.) and executions from
world-writable or ephemeral paths (/tmp, /var/tmp, /dev/shm, /var/run), which are frequently abused during container and
cluster lateral movement.
"""
false_positives = [
"""
Legitimate node health checks, diagnostics, or in-cluster agents may access the Kubelet API on port 10250. Validate
the calling process, command line, and whether the destination is the local node or another node.
""",
]
from = "now-9m"
index = ["auditbeat-*", "logs-auditd_manager.auditd-*", "logs-endpoint.events.network*"]
language = "eql"
license = "Elastic License v2"
name = "Kubelet API Connection Attempt to Internal IP"
note = """## Triage and analysis
### Investigating Kubelet API Connection Attempt to Internal IP
This alert indicates a process on a Linux host attempted to connect to port 10250 (Kubelet API) on an internal or
loopback IP address, including IPv4 private ranges and IPv6 localhost. Kubelet access is commonly abused to enumerate
pods, retrieve logs, or execute commands on nodes when authentication or network controls are weak.
### Possible investigation steps
- Review the initiating process (`process.*`) and its executable path; prioritize processes running from `/tmp`,
`/var/tmp`, `/dev/shm`, or `/var/run`, and suspicious interpreters or downloaders.
- Determine whether the destination IP is the local node, another node, or a management host, and whether connectivity to
10250 is expected for this workload/user.
- Correlate with process argument telemetry for HTTP URLs, kubelet endpoints (e.g., `/pods`, `/runningpods`, `/exec`), and
subsequent Kubernetes API audit activity or credential access.
### False positive analysis
- Approved troubleshooting (SRE/cluster operator) sessions that validate Kubelet reachability on the node.
- In-cluster agents that legitimately scrape or query the Kubelet (confirm vendor, image, and deployment).
### Response and remediation
- Restrict pod-to-node access to 10250 using network policies/security groups where possible.
- Rotate and revoke any exposed Kubernetes credentials and investigate for follow-on cluster discovery or execution.
"""
references = [
"https://attack.mitre.org/techniques/T1021/",
"https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/",
]
risk_score = 47
rule_id = "9f420cca-cb27-44db-a13d-c43c7b48e04a"
setup = """## Setup
### Auditd Manager: emitting network connection telemetry
This rule is written against `event.category:network` events. Elastic Defend provides this natively. For Auditd Manager,
you typically need to audit network-related syscalls (for example `connect`) and rely on the integration/pipeline to map
those syscall events into ECS-like network events.
If you are not seeing `event.category:network` for Auditd Manager data, add syscall audit rules for network connections.
The example below is a starting point and may need to be adjusted for your environment and noise tolerance:
```
# 64-bit
-a always,exit -F arch=b64 -S connect -S accept -S accept4 -S sendto -S recvfrom -k netconn
# 32-bit (if applicable)
-a always,exit -F arch=b32 -S connect -S accept -S accept4 -S sendto -S recvfrom -k netconn
```
After enabling, validate that events include `destination.ip`, `destination.port`, and a populated `process.*` context.
"""
severity = "medium"
tags = [
"Domain: Endpoint",
"Domain: Container",
"Domain: Kubernetes",
"OS: Linux",
"Use Case: Threat Detection",
"Tactic: Lateral Movement",
"Tactic: Discovery",
"Data Source: Elastic Defend",
"Data Source: Auditd Manager",
"Resources: Investigation Guide",
]
timestamp_override = "event.ingested"
type = "eql"
query = '''
network where host.os.type == "linux" and event.type == "start" and event.category == "network" and network.direction == "egress" and
event.action in ("connected-to", "connection_attempted") and (destination.port == 10250 or destination.port == 10255) and
cidrmatch(
destination.ip,
"127.0.0.0/8",
"10.0.0.0/8",
"172.16.0.0/12",
"192.168.0.0/16",
"169.254.0.0/16",
"100.64.0.0/10",
"::1/128",
"fc00::/7",
"fe80::/10"
) and
(
process.name in ("curl", "wget", "nc", "ncat", "netcat", "socat", "openssl", "perl", "busybox") or
process.name like ".*" or process.executable like "/*/.*" or
process.name like ("python*", "ruby*", "node*", "java*", "lua*", "apache*", "php*", "nginx", "httpd*", "lighttpd", "caddy", "mongrel_rails", "gunicorn",
"uwsgi", "openresty", "cherokee", "h2o", "resin", "puma", "unicorn", "traefik", "tornado", "hypercorn",
"daphne", "twistd", "yaws", "webfsd", "flask", "rails", "mongrel", "catalina.sh", "hiawatha", "lswsctrl") or
process.executable like ("/tmp/*", "/var/tmp/*", "/dev/shm/*", "/var/run/*", "/home/*", "/run/user/*", "/busybox/*")
)
'''
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1021"
name = "Remote Services"
reference = "https://attack.mitre.org/techniques/T1021/"
[rule.threat.tactic]
id = "TA0008"
name = "Lateral Movement"
reference = "https://attack.mitre.org/tactics/TA0008/"
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1613"
name = "Container and Resource Discovery"
reference = "https://attack.mitre.org/techniques/T1613/"
[rule.threat.tactic]
id = "TA0007"
name = "Discovery"
reference = "https://attack.mitre.org/tactics/TA0007/"