Detect Direct Cloud VM Connections in Splunk
Adversaries may leverage Valid Accounts to log directly into cloud-hosted virtual infrastructure using cloud-native connection methods. Cloud providers offer interactive console access to VMs that bypasses traditional network controls: Azure Serial Console, AWS EC2 Instance Connect, AWS Systems Manager Session Manager (SSM), and GCP OS Login. These methods authenticate via the cloud IAM layer rather than network credentials, can bypass firewall rules and security groups, and often provide SYSTEM or root-level access by default. Adversaries who compromise cloud IAM credentials can pivot to VM instances using these native APIs, even when SSH/RDP is blocked at the network level.
MITRE ATT&CK
- Tactic
- Lateral Movement
- Technique
- T1021 Remote Services
- Sub-technique
- T1021.008 Direct Cloud VM Connections
- Canonical reference
- https://attack.mitre.org/techniques/T1021/008/
SPL Detection Query
index=aws OR index=azure (sourcetype="aws:cloudtrail" OR sourcetype="azure:activity")
(
sourcetype="aws:cloudtrail"
eventName IN ("StartSession", "ResumeSession", "TerminateSession", "SendCommand",
"StartAutomationExecution", "SendSSHPublicKey", "StartSSHSession")
eventSource IN ("ssm.amazonaws.com", "ec2-instance-connect.amazonaws.com")
| eval UserARN='userIdentity.arn'
| eval TargetInstance=coalesce('requestParameters.target', 'requestParameters.instanceId')
| eval SourceIP='sourceIPAddress'
| eval AlertType="AWS_DirectVMConnection"
| table _time, UserARN, eventName, TargetInstance, SourceIP, AlertType
)
OR
(
sourcetype="azure:activity"
operationName.value IN ("MICROSOFT.COMPUTE/VIRTUALMACHINES/RUNCOMMAND/ACTION",
"MICROSOFT.SERIALCONSOLE/CONSOLESERVICES/ACCESS",
"MICROSOFT.COMPUTE/VIRTUALMACHINES/EXTENSIONS/WRITE")
| eval CallerUPN='caller'
| eval VMName='resourceId'
| eval SourceIP='httpRequest.clientIpAddress'
| eval AlertType="Azure_DirectVMConnection"
| table _time, CallerUPN, operationName.value, VMName, SourceIP, AlertType
)
| sort - _timeDetects direct cloud VM connections using two cloud log sources: AWS CloudTrail for SSM Session Manager operations (StartSession, SendCommand) and EC2 Instance Connect (SendSSHPublicKey), and Azure Activity Log for Serial Console access and Run Command operations. These cloud-native access methods are high-fidelity indicators of direct VM access outside normal channels.
Data Sources
Required Sourcetypes
False Positives & Tuning
- DevOps teams using SSM/Run Command for legitimate configuration management
- Cloud operations teams using Serial Console for VM troubleshooting
- Automated pipelines using cloud-native access methods for patching
- Emergency recovery procedures via serial console
- Managed service providers performing authorized maintenance
Other platforms for T1021.008
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1AWS SSM Send Command to EC2 Instance
Expected signal: AWS CloudTrail event: eventName=SendCommand, eventSource=ssm.amazonaws.com, with instanceId, documentName, and parameters. CloudWatch Log stream for the command output (if session logging enabled). Source IP address recorded in CloudTrail.
- Test 2AWS EC2 Instance Connect (Temporary SSH Key Injection)
Expected signal: AWS CloudTrail: SendSSHPublicKey event from ec2-instance-connect.amazonaws.com with instanceId, osUser, and publicKey fingerprint. Subsequent SSH connection attempt to the instance.
- Test 3Azure Run Command on VM
Expected signal: Azure Activity Log: MICROSOFT.COMPUTE/VIRTUALMACHINES/RUNCOMMAND/ACTION operation by the executing identity. The script content is visible in the Properties field. Source IP recorded in httpRequest.clientIpAddress.
- Test 4Start AWS SSM Session Manager Interactive Session
Expected signal: AWS CloudTrail: StartSession event from ssm.amazonaws.com with target instanceId, sessionId, and caller identity. Session logs in CloudWatch if session logging enabled. Note: interactive session content is only captured if session logging is configured.
References (7)
- https://attack.mitre.org/techniques/T1021/008/
- https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/serial-console-overview
- https://docs.aws.amazon.com/systems-manager/latest/userguide/session-manager.html
- https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Connect-using-EC2-Instance-Connect.html
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1021.008/T1021.008.md
- https://www.mandiant.com/resources/blog/sim-swapping-and-abuse-of-the-microsoft-azure-serial-console
- https://www.cisa.gov/news-events/cybersecurity-advisories/aa23-320a
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