Cloud Shared Responsibility
Cloud shared responsibility defines which security and operating duties belong to the provider and which remain with the customer for a particular service. Start with the actual service boundary, then assign each control to a person or team that can show evidence it works.
“Managed” describes a service offering; it does not name the owner of every setting, credential, data copy, or incident decision. The practical deliverable is a responsibility register connected to configuration and verification, not a slide with two colored halves.
TL;DR
- Map duties per service and deployment, rather than relying on an IaaS/PaaS/SaaS label alone.
- Keep customer identity, data handling, and application decisions explicit.
- Separate provider commitments from evidence your configuration satisfies them.
- Assign a customer owner for validating each inherited control.
- Revisit boundaries when changing service tier, integration, or operating model.
Quick Example
This complete Python illustration reviews fictional control records. “Provider” still needs a customer evidence reviewer; the code does not inspect a contract or cloud account.
The passing row only satisfies this tiny record-completeness rule. It does not establish that a patch is installed, that the provider meets an obligation, or that access is authorized.
Core Concepts
Service boundary
The provider’s duties change with the service selected. AWS’s model places EC2 guest operating-system and application patching with the customer, alongside security-group configuration. A managed service can move some infrastructure work across that boundary without transferring every workload duty. AWS shared responsibility
Control performer and accountable reviewer
Distinguish who performs a task from who decides the organization has adequate evidence. A provider may maintain a host while the customer verifies the service scope, applicable terms, reports, and remaining configuration. Naming a vendor as the performer does not resolve the customer’s acceptance decision.
Shared does not mean ambiguous
Some controls require coordinated actions: the provider supplies encryption features, while the customer chooses access policy and manages its relevant key responsibilities. Break the combined control into testable tasks. An incident can otherwise bounce between teams while each points to a correct but incomplete statement.
Turn the model into a service register
The table below is a suggested investigation guide. Confirm each row against the named service, current documentation, agreement, and deployment; it is not a contractual allocation.
Start with a real workflow such as uploading a report and sharing it with a colleague. Trace the identity provider, application, database, object storage, telemetry, and export path. At each handoff, ask who can change access and who will detect an incorrect decision. This reveals work that a product-level diagram tends to hide.
For patching, create separate rows for operating system, runtime, framework, library, container image, and application code where applicable. A provider update to its infrastructure does not update a dependency embedded in your build. Conversely, a team should not claim to patch an inaccessible managed host; it should verify the provider’s applicable process and address its own layers.
Verify the seams before accepting responsibility
A control statement needs both an intended rule and evidence from the configured system. For a storage-sharing rule, test an allowed identity and an identity that must be denied. Check direct access, exported copies, and cached credentials within the approved scope. A successful authorized read alone says little about the denial boundary.
For logging, trigger a harmless test event and follow it through collection, retention, search permissions, alert routing, and response ownership. Record delays and missing fields. A checkbox that says logging is enabled is only the beginning of that chain.
When evidence is unavailable, name the uncertainty precisely: unsupported audit scope, missing service tier, unclear customer setting, or untested integration. Ask the relevant provider or internal owner for the missing material. Do not convert an unknown into a completed control by placing it under the provider column.
Incident planning also needs a split. Define who can revoke credentials, isolate a workload, preserve records, contact support, restore data, and approve return to service. Give alternates access through the approved process before an incident. Avoid creating shared administrator credentials as a shortcut for unclear ownership.
Review the register after adopting a managed replacement. Work may move from host operation toward identity, data policy, application correctness, and vendor evidence. Budget for that changed work instead of assuming it disappears.
Best Practices
Attach a verification method to every duty
Use configuration review, observed behavior, provider evidence, or a combination appropriate to the control. Record what each method can establish. A document review cannot prove a workload’s current permission settings.
Keep acceptance and exceptions visible
Give unresolved gaps an owner, consequence, mitigation, and decision date. The person who accepts an exception should understand the affected data and service. Do not bury open work in a completed migration checklist.
Review changes at the boundary
New integrations, regions, identity providers, backups, support paths, and service tiers can alter responsibilities. Link the register to change review so the next deployment does not inherit an obsolete allocation.
Common Mistakes
Bad: Writing “the provider handles security” for a managed service.
Correct: Decompose the controls and identify the customer settings, data decisions, and application duties that remain.
Bad: Assigning two teams jointly without a decision owner.
Correct: Name the performer, evidence reviewer, and escalation authority for the individual task.
Bad: Treating a provider report as proof of the customer configuration.
Correct: Check the report’s scope and separately verify the deployed settings and behavior.
FAQ
Does shared responsibility change by service?
Yes. Use the specific service and deployment terms; broad service-model labels are useful starting points but incomplete operating instructions.
Who owns a provider-performed control internally?
Assign someone to validate applicable evidence and handle gaps. That reviewer does not perform inaccessible provider maintenance.
Is this a compliance assessment?
No. It is an engineering method for assigning and checking duties. Applicable legal, contractual, and compliance requirements need the relevant owners’ review.
Related Topics
- Cloud Computing — Locate workload and provider boundaries.
- Identity & Access Management — Verify identity and authorization duties.
- Application Security — Connect responsibility to concrete controls.