Auditing the Cloud: Navigating Shared Responsibility and Data Security in AWS, Azure, and GCP
Decoding the Shared Responsibility Model: A Cloud Security Minefield
Cloud computing has revolutionized the way organizations operate, offering unprecedented scalability, flexibility, and cost savings. However, the cloud also introduces new security challenges, particularly when it comes to understanding the shared responsibility model.
Cloud providers like Amazon Web Services (AWS), Microsoft Azure, and Google Cloud Platform (GCP) emphasize that security is a shared responsibility, but audits reveal that most organizations misunderstand the division of labor. This misunderstanding can lead to critical security gaps and increase the risk of data breaches.
Here’s a breakdown of the shared responsibility model:
AWS/Azure/GCP: The cloud provider is responsible for securing the infrastructure itself — the physical servers, networking equipment, virtualization hypervisors, and data centers that underpin their cloud services. They ensure the physical security of their facilities, protect against denial-of-service attacks, and maintain the availability of their core services.
You (the Customer): You are responsible for securing everything in the cloud — your data, applications, operating systems, access controls, and configurations. This includes implementing appropriate security measures to protect your virtual machines, storage buckets, databases, and other cloud resources.
Critical Audit Targets in the Cloud
As IT auditors, we must focus on the areas where organizations often struggle to meet their security responsibilities in the cloud. Here are some critical audit targets:
Misconfigured Storage Buckets: Publicly accessible storage buckets are a leading cause of data breaches in the cloud. Auditors should:
Use Open-Source Tools: Employ tools like Scout Suite or Cloud Security Suite to scan S3, Blob Storage, and Cloud Storage for public exposure.
Enforce Least Privilege: Ensure that storage buckets are configured with the principle of least privilege, granting access only to authorized users and applications.
Implement Data Encryption: Verify that sensitive data stored in cloud buckets is encrypted both in transit and at rest.
Review Access Logs: Regularly review access logs to identify any unauthorized access attempts or suspicious activity.
Finding: 41% of audited companies had at least one publicly readable bucket holding Personally Identifiable Information (PII), leading to data leaks.
2. Orphaned IAM Roles: Over time, IAM roles can become orphaned as employees leave the company or projects are completed. These orphaned roles can represent a significant security risk if they are not properly managed. Auditors should:
Audit Last-Used Timestamps: Analyze the last-used timestamps of IAM roles to identify those that are no longer active.
Enforce 90-Day Lifecycle Policies: Implement automated policies to automatically disable or delete inactive IAM roles after a certain period (e.g., 90 days).
Implement Role-Based Access Control (RBAC): Use RBAC to assign permissions based on job roles rather than individual users, simplifying access management and reducing the risk of privilege creep.
Conduct Regular Access Reviews: Periodically review IAM roles and permissions to ensure that they are still appropriate and necessary.
Finding: A financial services client had 1,200 inactive roles — 12% with administrative privileges, greatly widening their attack surface.
3. Encryption Gaps: Data encryption is essential for protecting sensitive information in the cloud. Auditors should:
Test Data-in-Transit: Verify that TLS 1.3 and FIPS 140–2 validated cryptographic modules are enforced for all data transmitted to and from the cloud.
Validate KMS Key Rotation: Ensure that encryption keys are regularly rotated to minimize the impact of a potential key compromise.
Assess Key Management Practices: Review the organization’s key management practices to ensure that encryption keys are securely stored and managed.
Enforce Encryption at Rest: Verify that all sensitive data stored in the cloud is encrypted at rest, using either cloud provider-managed keys or customer-managed keys.
Finding: One healthcare SaaS vendor used the same key for 4 years without rotation — a clear HIPAA audit failure and a major security risk.
Cloud-Specific Challenges and Considerations
Serverless (AWS Lambda, Azure Functions): Auditing serverless environments presents unique challenges. How are ephemeral functions logged and monitored? Ensure that the organization has implemented appropriate logging and monitoring mechanisms to track the execution of serverless functions and detect any suspicious activity.
Multi-Cloud Environments: Many organizations are adopting a multi-cloud strategy, using services from multiple cloud providers. This increases complexity and makes it more challenging to maintain a consistent security posture. Auditors should ensure that the organization has implemented a centralized security management platform to monitor and manage security across all cloud environments.
Compliance: Navigating the complex landscape of cloud compliance can be daunting. Auditors should understand the different compliance frameworks that are relevant to their organization (e.g., HIPAA, PCI DSS, GDPR) and ensure that cloud resources are configured to meet those requirements. Understand AWS Artifact, Azure Compliance Manager, and GCP Assured Workloads — and what frameworks align to each.
Auditor’s Cheat Sheet
Here’s a quick reference guide for auditing security in each of the major cloud providers:
AWS: Check GuardDuty findings, IAM Access Analyzer, and CloudTrail logs.
Azure: Audit PIM (Privileged Identity Management) activation logs, Azure Security Center recommendations, and Azure Monitor logs.
GCP: Validate VPC Service Controls bypass attempts, Security Command Center findings, and Cloud Logging data.
The Cost of Complacency: Real-World Breaches
A global e-commerce firm saved $185,000 per year in cloud costs after implementing audit recommendations — but more importantly, closed 9 critical risks before ransomware attackers exploited them. The firm was mismanaging IAM roles and had several public buckets. Audits are not just about compliance; they are about protecting your business.
