The argument
The Spreadsheet Cannot Segment the Network
A scope register should record a defensible conclusion from architecture and operating facts; it cannot substitute for the reasoning that produced the conclusion.
The field pattern
The inventory has an in-scope column with carefully maintained yes, no, and N/A values. The worksheet does not show that one “no” system administers the CDE, another supplies authentication, and a third shares a network path whose segmentation test belongs in a different folder.
Why it matters
Scope by Spreadsheet makes a conclusion look like a fact. That is especially fragile for connected-to and security-impacting systems whose relevance comes from what they can influence, administer, authenticate, monitor, or reach rather than what they store.
The spreadsheet can still be valuable—as an index into the scope argument. Each classification should point to the component, role, paths, dependencies, boundary, evidence, owner, and review date that make it defensible.
Questions that expose the Wack
- What architectural facts make this classification true today?
- Can the component connect to or affect the security of an in-scope system?
- Which segmentation or boundary evidence supports the exclusion?
- Who reviews the classification when connectivity, administration, or service use changes?