Ensuring Exclusive Bundling for TOP SECRET Cables
TOP SECRET cables must be in separate bundles or conduits to ensure security.
Plain language
This control is about keeping the communication cables that carry highly sensitive TOP SECRET information separate from others. It means they have their own individual space, so they’re safer from eavesdropping or interference. If this isn't done, there's a risk of the information being intercepted or tampered with, which could jeopardise critical operations or national security.
Framework
ASD Information Security Manual (ISM)
Control effect
Preventative
Classifications
TS
ISM last updated
Feb 2023
Control Stack last updated
19 Mar 2026
E8 maturity levels
N/A
Section
Cabling infrastructureOfficial control statement
TOP SECRET cables, when bundled together or run in conduit, are run exclusively in their own individual cable bundle or conduit.
Why it matters
If TOP SECRET cables share a bundle or conduit with other cabling, electromagnetic or physical access risks could enable compromise or tampering.
Operational notes
Inspect cable routes and conduits to confirm TOP SECRET cabling is in a dedicated bundle/conduit only, with no mixed-classification co-runs.
Implementation tips
- The IT team should review all existing cable setups to identify any TOP SECRET cables that need separating. They can do this by checking existing documentation and physically inspecting cable pathways. Update the infrastructure to ensure TOP SECRET cables have their own exclusive bundles or conduits.
- Facilities managers should work closely with the IT team when planning new installations to ensure TOP SECRET cables are always routed separately from others. During planning, use site diagrams to map out cable routes and allocate dedicated paths for sensitive data.
- Procurement officers should ensure that any contractors hired for cabling work understand the need for exclusive conduits for TOP SECRET cables. Include explicit requirements in contracts and discuss them during kick-off meetings with the contractor.
- IT security managers should develop a checklist that outlines the separation requirements for TOP SECRET cables. They should use this checklist during regular inspections to verify ongoing compliance with the control.
- Security officers should ensure that all staff are aware of the importance of not mixing cable bundles for different classification levels. This can be done through regular training sessions, providing examples of what can go wrong if this control is not followed.
Audit / evidence tips
-
Aska list of all cable routes within the organisation: Request specific layouts and marked pathways for TOP SECRET information cables
Goodshows each TOP SECRET cable has its own dedicated pathway
-
Askthe documentation of any installations or changes made to the cabling infrastructure: Check for notes on how this separation was maintained or improved
Goodincludes records of installations showing exclusive conduits for TOP SECRET cables
-
Askthe procurement contracts with cabling contractors: Look to ensure they include clauses about exclusive cabling requirements
Goodwould show contracts specifying requirements for separate conduits for sensitive data
-
AskCCTV footage or photographs of cable routes: Verify visually that TOP SECRET cabling is not mixed with other cables
Goodincludes recent images showing clearly separated cable bundles
-
Askto see training records related to this control: Request evidence of staff training on the importance of cable separation
Goodwould have records of recent sessions explaining why and how to maintain separate pathways
Cross-framework mappings
How ISM-1821 relates to controls across ISO/IEC 27001, Essential Eight, and ASD ISM.
ISO 27001
| Control | Notes | Details |
|---|---|---|
| layers Partially meets (1) expand_less | ||
| Annex A 7.12 | ISM-1821 requires TOP SECRET cables to be bundled or run in conduit exclusively (i.e., not sharing bundles/conduit with other cables) to ... | |
| handshake Supports (1) expand_less | ||
| Annex A 7.6 | ISM-1821 requires physical separation of TOP SECRET cabling by using dedicated bundles or conduits | |
These mappings show relationships between controls across frameworks. They do not imply full equivalence or certification.