Prevent Installation of TOP SECRET Cables in Shared Walls
In shared buildings, do not place TOP SECRET cables within walls shared with other spaces.
Plain language
This rule means that when you're setting up cables meant to carry top-secret information, they shouldn't be placed in walls that you share with other spaces or tenants. This matters because if those cables are put in shared walls, there's a risk that someone could tamper with them and access confidential information, potentially leading to leaks or security breaches.
Framework
ASD Information Security Manual (ISM)
Control effect
Preventative
Classifications
TS
ISM last updated
Nov 2021
Control Stack last updated
19 Mar 2026
E8 maturity levels
N/A
Section
Cabling infrastructureTopic
Cables in Party WallsOfficial control statement
In shared facilities, TOP SECRET cables are not run in party walls.
Why it matters
Running TOP SECRET cables in shared/party walls can allow unauthorised access, tampering or interception, leading to TOP SECRET compromise.
Operational notes
Confirm TOP SECRET cable routes avoid party walls during design and inspections; document paths and remediate any cabling found in shared walls.
Implementation tips
- Property managers should ensure that the building plans are reviewed before any cabling installation. Check that cable routes are clearly drawn, especially those carrying sensitive information, and confirm they do not intersect with shared walls.
- Project managers should work with architects and builders to design secure pathways for top-secret cables. This involves planning routes where cables are contained entirely within secure areas, such as private office spaces or dedicated corridors.
- Cabling contractors should be specifically briefed about the restriction against using shared walls. Make sure they have a copy of the guidelines and inspect the construction site to identify all shared walls and avoid them during installation.
- Office managers should arrange to have regular checks on existing cabling in shared facilities. This means setting up a maintenance schedule to inspect cable routes and ensure no unauthorised changes have been made.
- IT teams should label and document the routes of all top-secret cables. This involves keeping a detailed record in a secured database, with maps of the cable pathways and notes on compliance with the non-shared wall rule.
Audit / evidence tips
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Askthe floor plans and cabling layout documents. Check these documents for notes or markings showing that top-secret cables do not pass through shared walls
Goodshows clear evidence of routing decisions avoiding shared walls
-
Goodincludes dates, notes from inspections, and authorisations
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Askto see the contractor briefing documents. Verify that they include explicit instructions against using shared walls for top-secret cables and any receipts of acknowledgement from the contractor
Goodshows signed briefings with clear instructions
-
Goodincludes documented permissions with references to compliance checks
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Aska meeting record with all stakeholders involved in cabling design. Ensure the record includes discussions about routing paths and adherence to controls
Goodwill have minutes of meetings that mention decisions on maintaining security through cabling paths
Cross-framework mappings
How ISM-1133 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-1133 requires that, in shared facilities, TOP SECRET cables are not run in party (shared) walls to reduce the risk of compromise from... | |
These mappings show relationships between controls across frameworks. They do not imply full equivalence or certification.