Emerging Threats in Cloud Security: Understanding Bucket Hijacking
A newly identified attack vector targeting cloud storage has raised significant alarms among cybersecurity experts. This method, known as cloud bucket hijacking, exploits a fundamental architectural flaw that exists across all major cloud service providers, potentially jeopardizing sensitive data and resources.
The Nature of Cloud Bucket Hijacking
According to researchers from Palo Alto Networks’ Unit 42, the technique enables malicious actors to covertly divert active data streams—including audit logs, telemetry information, and other sensitive files—toward storage environments controlled by the attackers themselves. The most alarming aspect of this methodology is the minimal risk of detection, as the data streams continue to operate undisturbed.
This vulnerability affects leading cloud service platforms such as Google Cloud Platform (GCP), Amazon Web Services (AWS), and Microsoft Azure. The root of the issue lies in a common design choice: globally unique bucket names. In this context, the identity of a storage destination is strictly linked to its name, rather than to a permanent account owner. This creates a significant risk in the global namespace, whereby the possibility of naming conflicts can be exploited.
The Attack Sequence
The attack sequence initiates when an adversary gains access to a cloud environment and secures the necessary permissions to delete a target storage bucket. Following the deletion of the original bucket, the attacker swiftly creates a new bucket with the same name within their own external account.
The process sets off a catastrophic chain reaction. Automated data streams, such as replication pipelines, logging sinks, or transfer jobs previously configured to send data to the initial bucket, remain activated. Consequently, sensitive objects and audit events are rerouted directly to the adversary’s new bucket. The inherent stealth of this method is particularly concerning, as the operations of these automated processes continue without interruption, causing configurations to appear valid during standard security audits. Organizations may not recognize the breach until significant data exfiltration has occurred.
In their research, Unit 42 has successfully validated this attack methodology across different cloud ecosystems.
Google Cloud Findings
In the context of Google Cloud, researchers managed to simulate hijacking through various channels such as Cloud Logging sinks and Pub/Sub subscriptions, requiring only basic permissions (namely, storage.buckets.delete and storage.objects.delete) instead of intricate modification rights.
Amazon Web Services Insights
For Amazon Web Services, the technique proved effective when applied to Amazon Data Firehose and S3 bucket replication, resulting in the automatic routing of newly written objects to an externally controlled bucket.
Microsoft Azure Observations
Although Azure employs soft-delete policies that prevent immediate reuse of names across different tenants, attackers found ways to manipulate cross-subscription access, redirecting Azure Monitor diagnostic pipelines to unauthorized storage accounts within the same tenant.
A significant takeaway from the research is the prevalent assignment of broad storage administrator roles in enterprise settings. This commonly results in managers holding bucket deletion permissions, thereby allowing attackers to execute the hijacking tactic without requiring extensive permissions.
Proactive Defense Strategies
While Unit 42 has yet to observe the practical application of this attack technique in real-world scenarios, the challenge of post-execution detection underscores the importance of proactive defense measures. Security teams are strongly urged to enforce the principle of least privilege by minimizing bucket deletion permissions to essential administrative roles only. Specific recommendations include restricting storage.buckets.delete permissions in GCP, DeleteBucket rights in AWS, and Microsoft.Storage/storageAccounts/delete in Azure.
Additionally, organizations are advised to implement stringent data perimeter controls. For example, Google’s Virtual Private Cloud (VPC) Service Controls and AWS Service Control Policies (SCPs) can be employed to limit write operations to buckets outside trusted organizational boundaries.
AWS users should consider activating account-scoped regional namespaces for Amazon S3 to fully eliminate the risk of cross-account name reclamation. To enhance surveillance, organizations should set up high-severity monitoring alerts for all bucket-deletion API calls, utilizing Data Security Posture Management (DSPM) tools to prioritize the protection of sensitive data assets.
Conclusion
This study serves as a crucial reminder of potential vulnerabilities inherent in cloud security architecture. The design flaws discovered in one cloud ecosystem frequently provide attackers with potential pathways to exploit other platforms, reinforcing the necessity for comprehensive and integrated defense strategies across all multi-cloud configurations. As the landscape of cloud security evolves, organizations must remain vigilant and proactive in their efforts to safeguard against increasingly sophisticated threats.