ISO 27001 Annex A 8.20 Network Security

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What is ISO 27001 Network Security?

ISO 27001 Annex A 8.20 Network Security is an ISO 27001 control that requires us to secure our networks and document that we are doing so.


ISO 27001 Annex A 8.20 is a preventive control and a detective control to protect information in networks and its supporting information processing facilities from compromise via the network..


The ISO 27001 standard defines ISO 27001 Annex A 8.20 as:

Networks and network devices should be secured, managed and controlled to protect information in
systems and applications.

ISO27001:2022 Annex A 8.20 Network Security

Implementation Guide

This control is looking for us to have control over our networks. We are going to ensure the information security in networks and protect connected services from un authorised access. The are a few things to consider so lets go through them.


Documentation plays a large part in the standard and that is equally true of networks. This is usually an area where organisations struggle. Keeping up to date network documentation. But it is key to this control and passing the audit.

The documentation that is expected includes network diagrams and configuration files of devices. This documentation is also expected to have the document hygiene that includes document classification and version control. Again, this can often be overlooked.

Included in the documentation would be the classification level of the data that is carried over the network. As a rule, to simplify it, all organisation networks would be classed as confidential and public access / guest networks would be classified as public.

Roles and Responsibilities

Network management is a specialist activity that requires trained and experienced professionals. As a result you would document the roles and responsibilities including recording who is performing the role. Around this would be the usual access management processes of requesting, authorising and providing access as well as the segregation of duties to remove conflicts.

Logging and Monitoring

As part of the network implementation you will include appropriate logging and monitoring for actions that are relevant to information security.

Technical Considerations

Under advisement of your technical teams you will consider technical elements such as encryption of data in transit, restrictions and filtering of connections to the network and the use of firewalls, hardening of network devices, removal of default passwords and services, disabling vulnerable network protocols, authenticating systems on the network, segregating admin channels from other network channels.

Virtual Networks

Virtual networks can add an additional layer of security and appropriate security controls should be applied. There is a standard that covers Virtual Networks and it is ISO/IEC TS 23167.


ISO 27001

ISO 27001 Toolkit Business Edition

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. Can you show network diagrams, a list of devices and their configurations, logs of configuration changes, roles and responsibilities?

That you have have implemented Network Security appropriately

They will look at systems to seek evidence of network security. They will question you on the process and seek evidence that you have followed it. They want to see evidence of network security and the process in operation.

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 Toolkit Business Edition

Do It Yourself ISO 27001

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