ISO 27001 Annex A 8.22 Segregation of Networks

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What is ISO 27001 Segregation of networks?

ISO 27001 Annex A 8.22 Segregation of networks is an ISO 27001 control that requires us group information services and then put those groups on different networks. Ideally it wants information services, users and information systems on different networks but it is a little more nuanced than that, let’s take a look.

Purpose

ISO 27001 Annex A 8.22 is a preventive control to split the network in security boundaries and to control traffic between them based on business needs.

Definition

The ISO 27001 standard defines ISO 27001 Annex A 8.22 as:

Security mechanisms, service levels and service requirements of network services should be identified, implemented and monitored.

ISO27001:2022 Annex A 8.22 Segregation of Networks

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Implementation Guide

This control is really looking at large and complex networks. On the most part for small organisations you are going to have your main office network, possibly a public network, potentially a wifi network that ideally will be treated as public and operational networks will be handled by cloud service providers who you no doubt use. Still, let’s look at little more at the guidance.

At no point would this guide look to tell you how to implement a network and at all times I would say that you clearly need the services of a trained, experienced, network professional whose advice you should follow. As long as they adhere to the principles, you will be fine.

Choosing Network Domains

Breaking a network into domains is not something to do lightly. Every time you introduce a new domain you introduce a management overhead which you counter balance against the risk. Consider for the network domains things like trust levels, use, criticality, geography. There are many ways to crack an egg.

Take your time and think about this logically.

Network Types

The standard clearly is not only talking about physical wired networks but also virtual networks.

Network Perimeter

The area to focus on is the network boundary, this is the perimeter of the network. This is the part that protects the access into the main network. Like the door to a house. It should be secured. Where doors have keys you will consider firewalls, filtering, routing.

Who can gain access through the perimeter will take into consideration Access Control and the topic specific policy on Access Control.

To implement this you want a well defined boundary with well defined and implemented controls in place.

Wireless Networks

Where ever possible I would recommend that wireless networks are only ever used for public services, non critical data and traffic. It may be the case that you have to use them but they do come with a lot of disadvantages and challenges. You can potentially overcome them with compensating controls such as VPN, encrypted traffic and such like but they really want separating from the main networks. Take care when implementing wireless networks but do keep them segregated.

Access to networks and services

For this we consider what can and should be accessed and then have appropriate policy and process in place around that access.

ISO 27001 Annex A 5.15 Access Control

ISO 27001 Annex A 5.18 Access Rights

Authentication

The requirements on authentication for accessing services should be set.

ISO 27001 Annex A 5.17 Authentication Information

Authorisation

Procedures that determine who is allowed to access networks and services are to be put in place.

ISO 27001 Annex A 5.15 Access Control

Technical Controls

The network management and technical controls as well as the processes to access connections and services will be in place.

ISO 27001 Annex A 8.20 Network Security

Access Types

How access is carried out such as physical network, wireless network, VPN will be determined.

Monitoring and Logging

Recording the time, location and other appropriate logging attributes of users that access networks and services will be in place.

ISO 27001 Annex A 8.16 Monitoring Activities

Security Features

The security features of networks will be identified and implemented as well as documented. Consider here things like encryption, connection controls, cacheing, restrictive access. Firewalls, private networks, intrusion detection are also to be considered.

Network Security Professional

All in all you should work what a network security professional to work out the best solution for you and your needs. Your requirement is to identify, document, implement, monitor and review it.

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What will an auditor check?

The audit is going to check a number of areas. Lets go through the main ones

That you have documentation

What this means is that you need to show that you have documented your network, document your security implementation and put in place appropriate segregation.

That you have have implemented Segregation of Networks appropriately

They will look at systems to seek evidence of that it is implement appropriately. They will want to see evidence of the controls that in place and that they are operating. Network diagrams will be expected to be in place and reviewed.

That you have conducted internal audits

The audit will want to see that you have tested the controls and evidenced that they are operating. This is usually in the form of the required internal audits. They will check the records and outputs of those internal audits.

ISO 27001:2022 requirements

Organisational Controls - A5

ISO 27001 Annex A 5.1 Policies for information security

ISO 27001 Annex A 5.2 Information Security Roles and Responsibilities

ISO 27001 Annex A 5.3 Segregation of duties

ISO 27001 Annex A 5.4 Management responsibilities

ISO 27001 Annex A 5.5 Contact with authorities

ISO 27001 Annex A 5.6 Contact with special interest groups

ISO 27001 Annex A 5.7 Threat intelligence – new

ISO 27001 Annex A 5.8 Information security in project management

ISO 27001 Annex A 5.9 Inventory of information and other associated assets – change

ISO 27001 Annex A 5.10 Acceptable use of information and other associated assets – change

ISO 27001 Annex A 5.11 Return of assets

ISO 27001 Annex A 5.11 Return of assets

ISO 27001 Annex A 5.13 Labelling of information

ISO 27001 Annex A 5.14 Information transfer

ISO 27001 Annex A 5.15 Access control

ISO 27001 Annex A 5.16 Identity management

ISO 27001 Annex A 5.17 Authentication information – new

ISO 27001 Annex A 5.18 Access rights – change

ISO 27001 Annex A 5.19 Information security in supplier relationships

ISO 27001 Annex A 5.20 Addressing information security within supplier agreements

ISO 27001 Annex A 5.21 Managing information security in the ICT supply chain – new

ISO 27001 Annex A 5.22 Monitoring, review and change management of supplier services – change

ISO 27001 Annex A 5.23 Information security for use of cloud services – new

ISO 27001 Annex A 5.24 Information security incident management planning and preparation – change

ISO 27001 Annex A 5.25 Assessment and decision on information security events 

ISO 27001 Annex A 5.26 Response to information security incidents

ISO 27001 Annex A 5.27 Learning from information security incidents

ISO 27001 Annex A 5.28 Collection of evidence

ISO 27001 Annex A 5.29 Information security during disruption – change

ISO 27001 Annex A 5.31 Identification of legal, statutory, regulatory and contractual requirements

ISO 27001 Annex A 5.32 Intellectual property rights

ISO 27001 Annex A 5.33 Protection of records

ISO 27001 Annex A 5.34 Privacy and protection of PII

ISO 27001 Annex A 5.35 Independent review of information security

ISO 27001 Annex A 5.36 Compliance with policies and standards for information security

ISO 27001 Annex A 5.37 Documented operating procedures 

Technology Controls - A8

ISO 27001 Annex A 8.1 User Endpoint Devices

ISO 27001 Annex A 8.2 Privileged Access Rights

ISO 27001 Annex A 8.3 Information Access Restriction

ISO 27001 Annex A 8.4 Access To Source Code

ISO 27001 Annex A 8.5 Secure Authentication

ISO 27001 Annex A 8.6 Capacity Management

ISO 27001 Annex A 8.7 Protection Against Malware

ISO 27001 Annex A 8.8 Management of Technical Vulnerabilities

ISO 27001 Annex A 8.9 Configuration Management 

ISO 27001 Annex A 8.10 Information Deletion

ISO 27001 Annex A 8.11 Data Masking

ISO 27001 Annex A 8.12 Data Leakage Prevention

ISO 27001 Annex A 8.13 Information Backup

ISO 27001 Annex A 8.14 Redundancy of Information Processing Facilities

ISO 27001 Annex A 8.15 Logging

ISO 27001 Annex A 8.16 Monitoring Activities

ISO 27001 Annex A 8.17 Clock Synchronisation

ISO 27001 Annex A 8.18 Use of Privileged Utility Programs

ISO 27001 Annex A 8.19 Installation of Software on Operational Systems

ISO 27001 Annex A 8.20 Network Security

ISO 27001 Annex A 8.21 Security of Network Services

ISO 27001 Annex A 8.22 Segregation of Networks

ISO 27001 Annex A 8.23 Web Filtering

ISO 27001 Annex A 8.24 Use of CryptographyISO27001 Annex A 8.25 Secure Development Life Cycle

ISO 27001 Annex A 8.26 Application Security Requirements

ISO 27001 Annex A 8.27 Secure Systems Architecture and Engineering Principles

ISO 27001 Annex A 8.28 Secure Coding

ISO 27001 Annex A 8.29 Security Testing in Development and Acceptance

ISO 27001 Annex A 8.30 Outsourced Development

ISO 27001 Annex A 8.31 Separation of Development, Test and Production Environments

ISO 27001 Annex A 8.32 Change Management

ISO 27001 Annex A 8.33 Test Information

ISO 27001 Annex A 8.34 Protection of information systems during audit testing