8.22 Segregation of networks
Within its networks the organization is to keep groups of users, information services and information systems apart. Purpose: divide the network along security boundaries and control traffic between them according to business need. Guidance: consider managing large networks by splitting them into separate domains, each kept apart from the internet. Domains can be based on trust, criticality and sensitivity (for example public access, desktop and server domains, or low- and high-risk systems), on organizational units such as HR, finance or marketing, or on a mix, such as a server domain serving several units, and can be built with physically separate or logically separate networks. Each domain has a well-defined perimeter; where traffic between domains is allowed it passes through a gateway such as a firewall or filtering router. The criteria for dividing domains and the access permitted through gateways come from assessing each domain's security requirements against the access control policy (5.15), access needs and the value and classification of the information, taking into account the cost and performance impact of the gateway technology. Wireless networks need special handling because their perimeter is poorly defined: consider adjusting radio coverage, and in sensitive environments treat all wireless access as external, keeping it apart from internal networks until it has passed a gateway that applies the network controls (8.20). Guest wireless should be separated from staff wireless where staff use only controlled, policy-compliant devices, and guest WiFi should be at least as restricted as staff WiFi to discourage staff from using it. Other information: networks often extend beyond the organization through partnerships and shared facilities, raising the risk of unauthorized access to systems that need protecting from other network users.
Source: ISO/IEC 27002:2022, 8.22. 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 ISO/IEC 27002:2022 in the compliance library.
ISO/IEC 27002 is guidance on the Annex A controls; certification is against ISO/IEC 27001. Use this set when your sheet follows the 27002 numbering.
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
- Firewall or filtering router rules controlling traffic between domains, with rule review records · Cloud console / configuration management
- Configuration showing guest wireless separated from staff networks with restrictions at least as strict · Cloud console / configuration management
periodic reviewEvidence produced at each review
- Evidence that sensitive environments treat wireless as external and route it through a gateway · Cloud console / configuration management
- Segmentation testing results confirming that disallowed traffic between domains is blocked · Cloud console / configuration management
governing documentDocuments that govern the control
- Network segmentation design defining domains by trust, criticality, sensitivity or organizational unit, with the assessment that justified it · Policy repository / GRC workspace
- Diagrams and controls for connections to partner networks · Policy repository / GRC workspace
First move
Common gaps auditors find
- A flat network lets any workstation reach servers and management interfaces
- Guest WiFi has fewer restrictions than staff WiFi, so staff use it to bypass controls
- Inter-domain rules have become overly permissive 'any-any' rules
- Partner network connections land inside internal networks without a gateway
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.
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