The Global Namespace Risk: Universal Bucket Hijacking Technique for Cloud Data Exfiltration
Researchers identified a universal bucket hijacking technique affecting major cloud providers (AWS, GCP, Azure) that allows attackers to silently exfiltrate data streams. By exploiting the global uniqueness of bucket names, an attacker with deletion privileges can delete a target bucket and recreate it in their own environment, seamlessly rerouting logs, backups, and messages without requiring granular configuration update permissions.
Detection / HunterGoogle
What Happened
Security researchers have discovered a flaw in how major cloud providers like Amazon, Google, and Microsoft handle storage bucket names. Because these names must be unique globally, an attacker who gains permission to delete a company's storage bucket can immediately recreate a bucket with the exact same name in their own account. This tricks automated systems into sending sensitive data, like security logs or backups, directly to the attacker instead of the company. This issue affects organizations using automated cloud data streams. Companies should immediately restrict who has permission to delete cloud storage buckets and set up alerts for any bucket deletion events.
Key Takeaways
- A universal bucket hijacking technique allows attackers to silently reroute cloud data streams to external accounts.
- The attack exploits the global namespace uniqueness of storage buckets in AWS, GCP, and Azure.
- Attackers only need bucket deletion permissions (e.g., storage.buckets.delete) rather than granular stream update permissions to execute the hijack.
- Mitigation requires strict least privilege on deletion actions and implementing cloud data perimeters like VPC Service Controls or SCPs.
Affected Systems
- Google Cloud Platform (GCP) Cloud Logging, Pub/Sub, Storage Transfer Service
- Amazon Web Services (AWS) S3 Bucket Replication, Amazon Data Firehose
- Microsoft Azure Monitor
Attack Chain
An attacker compromises a cloud identity with permissions to delete storage buckets. The attacker identifies a bucket that serves as a destination for an automated data stream, such as a log sink or replication rule. The attacker deletes the victim's bucket and immediately recreates a new bucket with the exact same globally unique name within their own attacker-controlled cloud tenant. The automated data stream continues to operate, seamlessly routing sensitive data to the attacker's bucket without requiring the attacker to modify the stream's configuration.
Detection Availability
- YARA Rules: No
- Sigma Rules: No
- Snort/Suricata Rules: No
- KQL Queries: No
- Splunk SPL Queries: No
- EQL Queries: No
- Other Detection Logic: No
- Platforms: Cortex XSIAM
The article mentions that Cortex XSIAM has out-of-the-box rules to detect data movement to external buckets and alerts on high-severity storage deletion API calls, but no specific query logic is provided.
Detection Engineering Assessment
EDR Visibility: None — The attack occurs entirely within the cloud provider's control plane and APIs, which are not monitored by traditional endpoint detection and response tools. Network Visibility: None — The data exfiltration happens via backend cloud infrastructure (e.g., GCP Pub/Sub to GCS, AWS S3 replication), bypassing traditional corporate network perimeters. Detection Difficulty: Hard — The victim loses visibility into the destination bucket once it is recreated in the attacker's tenant. The only visible event in the victim's environment is the initial bucket deletion, which may blend in with legitimate administrative actions or automated cleanup scripts.
Required Log Sources
- Cloud Audit Logs
- AWS CloudTrail
- GCP Cloud Logging
- Azure Activity Logs
Hunting Hypotheses
| Hypothesis | Telemetry | ATT&CK Stage | FP Risk |
|---|---|---|---|
| Consider hunting for unexpected or unauthorized storage bucket deletion API calls, especially for buckets known to be destinations for log sinks or data replication. | Cloud Audit Logs | Execution | Medium to High, depending on the environment's use of ephemeral storage or automated infrastructure-as-code teardowns. |
| If you have visibility into cloud data perimeters, consider hunting for data streams or log sinks that are attempting to write to external or unknown tenant IDs. | Cloud Audit Logs | Exfiltration | Low, assuming strict data perimeters are enforced. |
Control Gaps
- Lack of strict least privilege on bucket deletion permissions
- Absence of cloud data perimeter controls (e.g., VPC Service Controls, AWS SCPs)
Key Behavioral Indicators
- Execution of storage.buckets.delete (GCP)
- Execution of DeleteBucket (AWS)
- Execution of Microsoft.Storage/storageAccounts/delete (Azure)
False Positive Assessment
- Low
Recommendations
Immediate Mitigation
- Verify against your organization's incident response runbook and team escalation paths before acting.
- Audit and restrict IAM permissions related to bucket deletion (e.g., storage.buckets.delete, DeleteBucket) to a minimal set of highly privileged administrative roles.
- Evaluate whether service accounts or applications possess unnecessary bucket deletion privileges and revoke them if not strictly required.
Infrastructure Hardening
- Consider implementing cloud data perimeter controls, such as AWS Service Control Policies (SCPs) or GCP VPC Service Controls, to restrict resource access to trusted organizational boundaries.
- If using AWS, evaluate enabling account regional namespaces for S3 buckets to eliminate the global namespace risk.
- Ensure critical data streams and log sinks are configured with robust monitoring to alert on destination unavailability.
User Protection
- Enforce multi-factor authentication (MFA) and strict conditional access policies for any identities holding storage administration roles.
Security Awareness
- Educate cloud architects and engineering teams on the risks of global namespace hijacking and the importance of least privilege for infrastructure lifecycle management.
MITRE ATT&CK Mapping
- T1530 - Data from Cloud Storage
- T1567.002 - Exfiltration Over Web Service: Exfiltration to Cloud Storage
- T1485 - Data Destruction
- T1562.001 - Impair Defenses: Disable or Modify Tools
