Beyond the Backup: The Hidden Dangers of Azure Snapshot Exfiltration

Understanding the threat landscape from an attacker’s perspective is crucial for strengthening cloud defenses. This article delves into the specifics of Azure disk snapshots, detailing their lifecycle, and potential vulnerabilities from an attacker’s viewpoint, and linking these stages to the MITRE ATT&CK framework to provide a comprehensive view of the tactics and techniques used.

Azure disk snapshots are point-in-time copies of virtual hard disks (VHDs) attached to Azure Virtual Machines (VMs). These snapshots capture the state and data of a disk at a specific moment and are primarily used for backup and recovery processes. They play a crucial role in disaster recovery strategies, allowing for the quick restoration of services following a failure or data corruption incident.

Creating and Managing Snapshots Using Azure CLI

The Azure Command-Line Interface (CLI) provides a powerful set of commands to manage Azure resources. To create a snapshot of a disk, you can follow these steps, as detailed in the Microsoft Azure documentation:

Identify the Disk:

First, you need to determine the disk you wish to snapshot. This can be done using: 

az vm disk list --resource-group myResourceGroup --vm-name myVM --output table

This command lists all disks attached to a virtual machine.

Create the Snapshot:

az snapshot create --resource-group myResourceGroup --name mySnapshot --source "/subscriptions/mySubscriptionId/resourceGroups/myResourceGroup/providers/Microsoft.Compute/disks/myDisk"

This command creates a snapshot from the identified disk.

Copy Snapshot to Storage Account: 

Following the steps outlined in Microsoft's guide, you can copy the snapshot to a storage account for retention or archival purposes. This process involves generating a SAS (Shared Access Signature) URL for the snapshot and using AzCopy to transfer the snapshot to a Blob storage account.  The detailed script and explanation can be found at Microsoft's Documentation on Copying Snapshots.

Attacker Motivation and Entry Points

From an attacker’s viewpoint, snapshots contain a goldmine of information, including sensitive data and system state, which can be exploited or sold. Gaining access to snapshots can be achieved through several vectors:

• Initial Access (MITRE Tactic: TA0001): Attackers may use spear-phishing to gain initial access to credentials that can manage Azure resources.

• Privilege Escalation (MITRE Tactic: TA0004): Once inside the network, attackers might exploit misconfigurations or vulnerabilities to gain higher privileges that allow snapshot access.

• Persistence (MITRE Tactic: TA0003): By creating new snapshots or accessing existing ones, attackers can maintain access to up-to-date data within the environment.

Techniques for Exfiltration

1. Cross-Account Snapshot Access:

   • Azure CLI Misuse: Attackers can use stolen credentials to execute Azure CLI commands to export snapshots to controlled storage accounts.

   • Defense Evasion (MITRE Tactic: TA0005): Modifying or deleting logs to hide their tracks, attackers can mask the unauthorized snapshot accesses.

2. Snapshot Export and Cloning:

   • Data Exfiltration (MITRE Tactic: TA0010): After gaining access, attackers can clone snapshots to their own Azure accounts or export them to external storage solutions, effectively exfiltrating sensitive data outside the organization.

To protect against unauthorized snapshot access and exfiltration, consider the following steps:

• Implement Strict Access Controls: Use Azure role-based access control (RBAC) to restrict who can create and access snapshots.

• Encrypt Snapshots: Apply encryption to your snapshots to protect data at rest.

• Regular Audits: Perform regular security audits and reviews of your Azure environment to ensure compliance with security policies and to identify potential misconfigurations.

• Incident Response: Develop a robust incident response plan that includes scenarios for dealing with unauthorized snapshot access.

 

Conclusion

Azure disk snapshots, while invaluable for data protection and recovery, can also pose a security risk if not properly managed. Understanding the full lifecycle of snapshots,from creation, management, and potential exfiltration pathways, is crucial for maintaining a secure Azure environment. By following best practices for security and utilizing tools such as Azure CLI for efficient snapshot management, organizations can safeguard their data against emerging threats.

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