Mythos Hardening Control · MRIS 2.0 · Applies to ISO/IEC 27001 and IT-Grundschutz

MHC-07 Multi-tenancy isolation with demonstrable separation

Enforces demonstrable separation between tenants – a compromised tenant does not become a springboard to others; effectiveness is proven by separation tests, not merely asserted.

At a glance

Operational benefit: demonstrably prevents an attacker who gains a foothold in one tenant from reaching across to the data of other tenants — the damage remains confined to one tenant.
Policy affected: policy on secure architecture and tenant separation (for multi-tenant services).
Dependencies: no precondition; concerns organizations running several customers on a shared platform; makes use of key separation (relation to A.8.24) and network separation.
Effort drivers: depends on the architecture model (shared versus separate resources) and the number of tenants. The actual effort depends on the organization's resources.
Primary metric: outcome of regular, ideally automated separation tests (no cross-tenant access demonstrable).
Standards touched (no claim of fulfilment): ISO/IEC 27002 A.8.22/A.5.23; C5:2026 OPS-30/31, PSS-10; CSA Cloud Controls Matrix.

Control statement

In multi-tenant services, data, networks and compute resources are separated per tenant; the separation is documented and demonstrably implemented — not merely asserted conceptually. Advanced hardening (Managed level): regular evidence of the separation through tests that are automated so far as possible.

Purpose and threat relevance

In multi-tenant services, many customers share a common platform. If an attacker succeeds in gaining a foothold in one tenant, the central question is whether they can reach across from there to the data of other tenants. AI-supported attackers search systematically for precisely such gaps in the separation. Conceptual separation alone is not sufficient; what matters is that the separation actually takes effect and that this is evidenced. The protective objective is to confine the damage of an attack demonstrably to a single tenant.

Effect across frameworks

These are the controls and requirements the MHC acts on. The classification shows how much each control loses its effect under AI-enabled attacks.

Effect across frameworks
Number	Title	Classification / Level
ISO/IEC 27001:2022, Annex A 2 controls
A.5.23	Information security for use of cloud services	partially degraded
A.8.22	Segregation of networks	partially degraded
IT-Grundschutz, MRIS.bd 1 requirements
MRIS.bd.2.3.A3	Implementing Verifiable Tenant Separation	elevated protection needs

All 93 controls in the analysis matrix · All 23 requirements of the module family

Maturity path

Initial: logical tenant separation documented.
Defined: tenant-specific keys; network and resource separation implemented.
Managed: demonstrable separation through automated tests; regular audits.

Measurement and audit evidence

Metric: outcome of the regular separation tests (no cross-tenant access demonstrable); frequency and coverage of the tests.
Stage gate (guide value): one passed, documented tenant separation test per level (Initial annually, internally; Defined per major release; Managed additionally by independent third parties). Evidence recorded in project controlling (MRIS Chapter 10.6).
Evidence: separation concepts, test records, remediation evidence for identified weaknesses.
Evidence logic (following ISO/IEC 27001, Clause 9): documented? — separation concepts and test records; responsible? — architecture or operations lead; frequency? — regular tests; tolerance? — no demonstrated cross-tenant access.

Typical mistakes

The separation is described only conceptually but never evidenced through tests.
Data separation is implemented but network or resource separation is not — the breach occurs via the unprotected path.
Tests examine only the normal case, not the deliberate circumvention attempt from within a tenant.
On extensions (new functions, new tenants) the separation is not re-examined.

Delimitation and residual risk

Delimitation: concerns the separation between tenants; the protection of the processing itself is dealt with by MHC-06, and the identity of the workloads by MHC-04.
Residual risk: a shared platform retains a common underlying layer; flaws in that common layer can affect several tenants despite the separation.
ISO/IEC 27002:2022 (indirectly): A.8.22 Segregation of networks; A.5.23 Information security for use of cloud services.
Framework: C5:2026 OPS-30/31 (data separation), PSS-10 (software-defined networking); CSA Cloud Controls Matrix; supplementary ISO/IEC 27017 (cloud services).

Implementation in detail

Organizational and technical implementation, implementation examples and the prioritization within the overall programme are described in the Implementation Guide.

Implementation Guide (PDF)Back to the MHC catalog