“The cloud is secure — but only if you secure your slice.”
—Every provider’s fine print

Modern SaaS companies thrive on cloud speed and elasticity, yet many overlook a fundamental truth: security in the cloud is a shared game. Knowing exactly which duties belong to the provider and which remain yours is the fastest way to avoid headline‑grabbing breaches — and to breeze through customer audits.

This guide demystifies the Shared‑Responsibility Model (SRM), compares how AWS, Azure, and Google Cloud implement it, and equips you with a checklist and RACI matrix you can drop straight into your security program.

What is the Shared‑Responsibility Model?

At its core, the SRM divides cloud security into two buckets:

Responsibility	Cloud Provider	Customer
Security of the cloud	Physical datacenters, global network, hardware, virtualization layer	—
Security in the cloud	—	OS patching, IAM, encryption keys, application code, data

Providers guarantee that racks stay locked and hypervisors are hardened. You must lock down identities, configure networks, encrypt data, and monitor everything above the hypervisor.

Visual Cheat‑Sheet

Service Model	Examples	Responsibility Distribution
SaaS	AWS WorkMail, Microsoft 365, Google Workspace	Provider: Most security controls Customer: Minimal (user access, data)
PaaS	AWS RDS, Azure SQL Database, Google Cloud SQL	Provider: Platform & infrastructure Customer: Moderate (configuration, access, data)
IaaS	AWS EC2, Azure Virtual Machines, Compute Engine	Provider: Infrastructure only Customer: Significant (OS, apps, data, network, IAM)

Rule of thumb: The closer you are to IaaS, the more security controls you own.

Five Dangerous Misconceptions

1. “My provider encrypts everything by default.”
   Encryption is often available but rarely enforced; you must flip the switch and manage the keys.
2. “Serverless means no ops.”
   You still manage IAM roles, secrets, and runtime dependencies for Lambda/Functions/Cloud Functions.
3. “Provider compliance certs cover me.”
   Auditors still test your controls; SOC 2 isn’t transferrable.
4. “Snapshots are automatic backups.”
   Without lifecycle policies and cross‑region replication, they don’t satisfy DR requirements.
5. “CI/CD pipelines inherit SRM.”
   Build systems often run outside provider guarantees — lock down runners and artifact stores yourself.

Executive Checklist: Own Your Slice

Check these items quarterly to stay in the green:

• Root credentials locked behind MFA hardware tokens.
• Least‑privilege IAM roles reviewed; stale keys rotated or deleted.
• Network boundaries: no broad 0.0.0.0/0 security‑group rules in prod.
• Data encryption enabled at rest & in transit; CMKs rotated annually.
• Patch cadence defined for OS, containers, and third‑party libs.
• Centralized logging & SIEM ingesting CloudTrail / Activity Logs.
• Automated backups & DR drills meet RTO/RPO targets.
• Incident response runbooks mapped to NIST 800‑61 phases.

Download the full RACI spreadsheet here ➡️ link to lead magnet.

Mapping SRM to NIST CSF 2.0

The NIST Cybersecurity Framework (CSF) 2.0, released in February 2024, provides an ideal structure for implementing shared responsibility. By mapping your cloud controls to each CSF function, you create a comprehensive approach that satisfies both security and compliance requirements.

CSF Function	Shared‑Responsibility Focus	Provider Handles	Customer Handles
Govern	Define RACI, set policy, monitor metrics	Framework documentation, compliance certifications	Security steering committees, cloud governance policies
Identify	Inventory assets per account/subscription	Resource metadata APIs, billing reports	Implementing tagging strategies, data classification
Protect	IAM, encryption, network segmentation	Identity services, encryption APIs, VPC tools	Role design, key management, security group rules
Detect	Log collection, anomaly detection, alerts	CloudTrail/Activity Logs, monitoring services	SIEM integration, alert tuning, vulnerability scanning
Respond	Automated containment actions, playbooks	Security services, auto-remediation APIs	Incident response playbooks, ChatOps integrations
Recover	Tested backups, region fail‑over plans	Snapshot services, cross-region replication	DR testing, RTO/RPO validation, post-incident reviews

Why Combine SRM With CSF 2.0?

1. Better audit evidence: Map provider responsibilities and your controls to each CSF category for streamlined SOC 2 reporting
2. Clearer conversations: Use CSF’s structured approach to explain your cloud security posture to stakeholders
3. Continuous improvement: Regularly evaluate which responsibilities shift as you adopt new cloud services

Pro tip: Implement policy-as-code guardrails (e.g., AWS Config, Azure Policy, OPA) to automatically enforce your share of the model. Learn more in our NIST CSF 2.0 implementation guide.

Using the CSF lens clarifies which tasks must be documented for external auditors or customer security questionnaires, while helping your team understand exactly where provider responsibility ends and yours begins.

Conclusion & Next Steps

The Shared‑Responsibility Model isn’t marketing fluff—it’s the contract that keeps cloud workloads safe. Mastering where provider security ends and yours begins lets you invest effort where it counts, impress auditors, and sleep easier.

Need an expert eye on your SRM gaps?
Book a free 30‑minute architecture review with an nScope security architect and receive a customized “You vs. Cloud” RACI sheet.

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