What evidence do auditors commonly ask for on COS-06 Segregation of data traffic in jointly used network environments?

Documented tenant segregation concept for shared network environments; Network configuration listing the per-tenant identifiers currently in use; Test results demonstrating traffic cannot pass between two tenant segments; Controls preventing a retired tenant identifier from being handed to another customer.

What is the most common gap auditors find on COS-06?

Separation depends on application logic rather than measures taken at network level

BSI C5 (121-criteria catalogue) · C5: Communication Security

`COS-06` Segregation of data traffic in jointly used network environments

Segregate the traffic of different cloud customers in shared network environments at network level following a documented segregation concept, so transmitted data retains its confidentiality and integrity between tenants.

Source: BSI C5 (121-criteria catalogue), COS-06. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open BSI C5 (121-criteria catalogue) in the compliance library.

The edition of the catalogue is not stamped here; check the edition your attestation is issued against.

artefacts

held by a system

at each review

moderate

to go live

Cloud console / configuration management

where the evidence lives

teal = a system already holds it · olive = produced at each review. To go live: easy when half or more of the artefacts are already held by a system, moderate from a quarter to a half, hard below a quarter.

These are the artefacts auditors commonly ask for on this requirement, our guidance rather than text from the standard. Your assessor decides what is sufficient in your context, and asks for samples across the period when a report covers one.

system holds itEvidence a system already holds

Network configuration listing the per-tenant identifiers currently in use · Cloud console / configuration management

periodic reviewEvidence produced at each review

Test results demonstrating traffic cannot pass between two tenant segments · Source control / CI pipeline

governing documentDocuments that govern the control

Documented tenant segregation concept for shared network environments · Policy repository / GRC workspace
Controls preventing a retired tenant identifier from being handed to another customer · Policy repository / GRC workspace

First move

Start with the 1 of 4 artefacts that already live in a system (Cloud console / configuration management); keep the periodic reviews but log each one as a dated record with a named reviewer.

Common gaps auditors find

Separation depends on application logic rather than measures taken at network level
Identifiers recycled after decommissioning, allowing traffic to surface in the wrong tenant
A shared services segment lets tenants observe one another's traffic

Do this for your whole sheet

Paste the rows you run your controls from and get this mapping for every control at once, with the periodic-review ones flagged and a first move per row. No account for the first run.

Build my evidence sheet

COS-05 Networks for administration · COS-07 Documentation of the network topology