ISO 27001 Annex A 8.17 Clock Synchronisation

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What is ISO 27001 Clock Synchronisation?

ISO 27001 Annex A 8.17 Clock Synchronisation is an ISO 27001 control that requires us to ensure the all the clocks of all systems are synchronised to an approved time source.

Purpose

ISO 27001 Annex A 8.17 is a detective control to enable the correlation and analysis of security-related events and other recorded data, and to support investigations into information security incidents.

Definition

The ISO 27001 standard defines ISO 27001 Annex A 8.17 as:

The clocks of information processing systems used by the organisation should be synchronised to approved time sources.

ISO27001:2022 Annex A 8.17 Clock Synchronisation

Implementation Guide

The whole point of this control is so that everything is synchronised and that it is reporting and recording and using the same time. This information is used in information security incidents and at the most extreme case in investigations. It is part of evidence gathering and would need to be in place for criminal investigations.

The advice here would be to speak with your technical teams on the best approach and best technology to use.

The need may arise from legal, regulatory, statutory, contractual, standards and internal monitoring needs. So this would be the first place to look to see if there is anything specific that you need to do.

The basic premise is to get all clocks of all devices on the same page. This includes things you might not consider such as building entry systems or surveillance systems.

It is probably more practical to have all devices of a type synced to the same source rather than every device of every type connected to the same source. Some systems may use there own time source for example. A clock for each service is acceptable with any difference recorded in order to mitigate the risk of discrepancies.

The advice of the standard talks of linking to a radio time broadcast from a national atomic clock or global positioning system (GPS) and protocols such as networking time protocol ( NTP ) or precision time protocol (PTP) to keep all networked systems in synchronisation with a reference clock.

For small organisations a lot of this can be overkill and it would be the advice to pursue the most technically simple option available.

ISO 27001 Toolkit

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 clock synchronisation. This may be just recording what you do but be sure to understand how your clocks are synchronised and be able to show it.

That you have have implemented clock synchronisation appropriately

They will look at systems to seek evidence of clock synchronisation. They want to see evidence of clock synchronisation and the process in operation. It maybe that they look for evidence that you have used it as part of information security incident management.

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.

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ISO 27001:2022 requirements

ISO 27001:2022 Annex A 5 - Organisational Controls

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 

ISO 27001:2022 Annex A 8 - Technology Controls

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