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Communications infrastructure
ASD ISMISM-1133

ASD ISM 1133 Prevent installation of TOP SECRET cables in shared walls

What it says

In shared facilities, TOP SECRET cables are not run in party walls.

Quoted as published. Everything else on this page is written by Control Stack.

What it means

In plain English

In shared buildings, do not place TOP SECRET cables within walls shared with other spaces.

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.

Why it matters

Running TOP SECRET cables in shared/party walls can allow unauthorised access, tampering or interception, leading to TOP SECRET compromise.

How to implement

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

Keep it running

Confirm TOP SECRET cable routes avoid party walls during design and inspections; document paths and remediate any cabling found in shared walls.

Evidence and audit

  1. Check 1 of 5What an auditor asks for

    Ask for

    The floor plans and cabling layout documents. Check these documents for notes or markings showing that top-secret cables do not pass through shared walls.

    Good evidence

    Shows clear evidence of routing decisions avoiding shared walls.

  2. Check 2 of 5What an auditor asks for

    Look at

    Regular entries documenting checks and any maintenance conducted on cable routes, specifically noting adherence to the non-shared wall policy.

    Good evidence

    Includes dates, notes from inspections, and authorisations.

  3. Check 3 of 5What an auditor asks for

    Ask for

    To 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.

    Good evidence

    Shows signed briefings with clear instructions.

  4. Check 4 of 5What an auditor asks for

    Look at

    Evidence of review and authorisation before any alterations are made to cabling routes.

    Good evidence

    Includes documented permissions with references to compliance checks.

  5. Check 5 of 5What an auditor asks for

    Ask for

    A meeting record with all stakeholders involved in cabling design. Ensure the record includes discussions about routing paths and adherence to controls.

    Good evidence

    Will have minutes of meetings that mention decisions on maintaining security through cabling paths.

Mappings

Closest match in ISO/IEC 27001: A.7.12, Secure cabling for power and data, which this control partially meets.

ISO 27001

ISO/IEC 27001: 1 mapping

  • A.7.12Secure cabling for power and dataPartially meets

Mappings show how controls relate across frameworks. They do not imply full equivalence or certification.