In this guide you will learn how to implement ISO 27001 Annex A 5.15 Access Control and pass your audit from ISO 27001 Lead Auditor Stuart Barker – author of the ultimate ISO 27001 Toolkit.
ISO 27001 Annex A 5.15 is an ISO 27001 control that requires an organisation to implement the control of access to information and other assets based on business and information security requirements.
Table of contents
- Purpose & Definition
- FREE ISO 27001 Annex A 5.15 Training Video
- Implementation Guide
- How to implement ISO 27001 Annex A 5.15
- 1. Formalise the Access Control Policy
- 2. Map Roles to the Asset Register
- 3. Standardise User Registration and De-registration
- 4. Provision Access via Role-Based Access Control (RBAC)
- 5. Segregate Privileged Access Rights
- 6. Enforce Strong Authentication and MFA
- 7. Configure Resource-Level Restrictions
- 8. Execute Quarterly User Access Reviews
- 9. Automate Account Adjustment for Movers
- 10. Document the Control Environment in an ROE
- How to comply
- What the auditor will check
- Top 3 Mistakes People Make and How to Avoid Them
- ISO 27001 Annex A 5.15 FAQ
- Related ISO 27001 Controls and Further Reading
- ISO 27001 controls and attribute values
Purpose & Definition
The purpose of ISO 27001 Annex A 5.15 is a preventive control that ensures authorised access and to prevent unauthorised access to information and other associated assets.
The ISO 27001 standard defines ISO 27001 Annex A 5.15 as:
Rules to control physical and logical access to information and other associated assets should be established
ISO/IEC 27001:2022 Annex A 5.15 Access Control
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FREE ISO 27001 Annex A 5.15 Training Video
In this free training video you will learn How to implement ISO 27001 Access Control (Annex A 5.15) and Pass Your Audit.
Implementation Guide
The control of access to information and other assets is going to require a topic specific ISO 27001 Access Control Policy. To implement control of access you are going to have to first identify what you have. We cannot control it if we do not know we have it so before you move on to access control be sure first to have completed your asset registers. We covered asset inventories in ISO 27001 Annex A 5.9 Inventory Of Information And Other Associated Assets.
Once you know what you have you are going to implement information classification which we covered in ISO 27001 Annex A 5.12 Classification Of Information. This is going to set out the classification levels of the organisation and the controls and restrictions for each classification.
The standard wants you to implement access control rules by defining and mapping appropriate access rights and restrictions to relevant entities. What it means by entities is the things that are doing the access which includes humans and also logical items such as services, devices and machines.
Access Control Principles
The principles on access control usually fall in to mainstream camps of thinking. They are:
Need to know
Need to know is the principle that you grant access to the information required to perform the tasks and duties.
Need to use
Need to use is the principle of granting access where a clear need is present
Let’s be fair the difference is subtle and barely material in that you grant access to what people need. You will not be quizzed on this and a simpler way to look at it is, do not give people access to things they don’t need.
Access Control Methodologies
There is no one right way to implement access control although the most common is role based access. It is the most common as it most often the most simple. The list of access control methodologies is
- MAC – mandatory access control
- DAC – discretionary access control
- RBAC – role based access control
- ABAC – attribute based access control
Access Control Granularity
The level of granularity of access control is based on your business and business risk. It is a wide range with examples of covering entire networks or systems all the way down to restricting access to individual fields. You can consider factors such as locations or how people connect or who connects from teams to individuals.
The level of granularity has a direct correlation on cost and security.
The more granular you are the more cost you will incur in time and resources but the more secure you will be.
The less granular you are then the less cost in time and resources but the more insecure (potentially) you will be.
The art is to find the balance that is right for you.
Considerations when implementing access control
Let us take a look at considerations when defining and implementing access control rules
- Working to the principle of least privilege which means we restrict access to everything unless needed as opposed to the principle of everyone has access to everything unless forbidden.
- Account for automation in process and technology where permissions are changed automatically
- Implement a review of the approval processes at least annually or based on significant change
- It is important to ensure we are consistent in our approach to both access rights and information classification
- Physical perimeter security should be considered if it is appropriate and to be consistent with access rights
- Where dynamic access control is in play to consider the factors and elements and how they can be reflected
Steps in implementing access control
You are going to have to
- Establish and communicate a topic specific ISO 27001 Access Control Policy
- Complete your physical and virtual asset register
- Complete your data asset register
- Decide on your access control methodology / approach
- Implement your access control
Access Control Policy Template
The access control policy sets our your approach to access control.
How to implement ISO 27001 Annex A 5.15
Implementing ISO 27001 Annex A 5.15 is about more than just setting passwords: it is about governing the entire lifecycle of access to your organisation’s information assets. As a Lead Auditor, I expect to see a robust framework where access is granted based on business necessity and strictly enforced through technical controls. Follow these ten steps to build a compliant and secure access control environment.
1. Formalise the Access Control Policy
Create a comprehensive policy document that defines the rules for both logical and physical access across the organisation. This policy serves as your “Source of Truth” during an audit and must be approved by senior management. Requirements include:
- Defining access rules based on the “Need to Know” and “Least Privilege” principles.
- Establishing clear guidelines for different classifications of information.
- Distinguishing between standard user access and administrative privileges.
2. Map Roles to the Asset Register
Consult your Asset Register to identify every information asset and its respective owner. This step ensures that access is authorised by the person responsible for the data, rather than IT acting in isolation. Requirements include:
- Identifying all software, hardware, and data assets within the ISMS scope.
- Assigning an Asset Owner to every entry in the register.
- Documenting which job roles require access to specific assets to perform their duties.
3. Standardise User Registration and De-registration
Establish a formal workflow for the onboarding and offboarding of employees, contractors, and third parties. This process prevents “Shadow Access” where accounts are created without proper oversight. Requirements include:
- Implementing a Joiner process that verifies identity before provisioning unique IDs.
- Ensuring a Leaver process that revokes all access immediately upon termination of employment.
- Maintaining a Record of Evidence (ROE) for all registration and de-registration activities.
4. Provision Access via Role-Based Access Control (RBAC)
Use an RBAC model to provision access rights based on job functions rather than individual requests. This ensures consistency and reduces the risk of excessive permissions. Requirements include:
- Creating IAM (Identity and Access Management) roles that mirror organisational positions.
- Ensuring that access is only provisioned after formal authorisation from the Asset Owner.
- Verifying that temporary access for contractors is set to expire automatically.
5. Segregate Privileged Access Rights
Strictly control accounts with elevated permissions, such as Domain Admins or Superusers, as these represent the highest security risk. Privileged access must be handled via a separate, audited process. Requirements include:
- Provisioning dedicated administrative accounts that are separate from standard user accounts.
- Restricting privileged access to the absolute minimum number of individuals.
- Implementing a “Just-In-Time” (JIT) access model for sensitive configuration changes.
6. Enforce Strong Authentication and MFA
Implement technical controls to verify the identity of users attempting to access the network. Multi-Factor Authentication (MFA) is a mandatory requirement for remote and privileged access. Requirements include:
- Mandating MFA for all external access via VPN or cloud services.
- Setting minimum password complexity and rotation requirements in line with industry standards.
- Prohibiting the use of shared or generic accounts for any information asset.
7. Configure Resource-Level Restrictions
Apply technical “Read, Write, and Delete” permissions at the file and database level to enforce the policy. This ensures that even if a user is on the network, they can only interact with data relevant to their role. Requirements include:
- Configuring Access Control Lists (ACLs) on all file servers and cloud storage.
- Restricting access to specific applications and functions based on user roles.
- Verifying that “Everyone” or “Guest” access is disabled on all internal resources.
8. Execute Quarterly User Access Reviews
Perform regular “re-certification” of user access rights to ensure permissions remain appropriate as the organisation evolves. This is a critical check for an ISO 27001 auditor. Requirements include:
- Distributing user lists to Asset Owners for periodic verification and sign-off.
- Removing access for any users who no longer have a valid business requirement.
- Documenting the review process and the results in an Audit ROE.
9. Automate Account Adjustment for Movers
Update access rights immediately when an individual changes roles within the organisation to prevent “Privilege Creep.” This ensures that old permissions are removed when they are no longer needed. Requirements include:
- Triggering an access review whenever a user’s department or job title changes in HR systems.
- Revoking old permissions before granting new ones to ensure “Least Privilege.”
- Reviewing and adjusting physical access rights (e.g., key cards) for internal movers.
10. Document the Control Environment in an ROE
Maintain a centralised Record of Evidence (ROE) that proves your access controls are functioning as intended. Without documentation, you cannot prove compliance to an external auditor. Requirements include:
- Collecting logs of account creation, modification, and deletion.
- Storing signed authorisation forms and quarterly review sign-offs.
- Maintaining a history of MFA enrolment and privileged access logs for at least 12 months.
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How to comply
To comply with ISO 27001 Annex A 5.15 you are going to implement the ‘how’ to the ‘what’ the control is expecting. In short measure you are going to
- Implement and ISO 27001 Access Control Policy
- Complete your physical and virtual asset register
- Complete your data asset register
- Decide on your access control methodology / approach
- Implement your access control
What the auditor will check
The audit is going to check a number of areas. Lets go through the most common
1. That you have not done something stupid
The auditor is going to check the rules, procedures and access control methodolgy and make sure you followed them. As with everything having documented evidence of anything you can is going to be your friend. So practical things like asset registers, access control procedures that you can evidence are in operation, reviews of access. Work through recent hires for example and ensure the processes were followed and look for the gotchas. Is there an approval audit trail. When you log into the system that was approved does the users access match what was requested
2. That you have rules, processes and you have followed them and have trained people
This is obvious but they are going to look that you have documented what you say you do, that you follow it and that you have trained people. The biggest gotcha here is having people with access that have left. In other words you didn’t have or follow a leaver process and so people’s access remain even though their contract has ended.
3. Documentation
They are going to look at audit trails and all your documentation and see that is classified and labelled. All the documents that you show them, as a minimum if they are confidential should be labelled as such. Is the document up to date. Has it been reviewed in the last 12 months. Does the version control match. Doing anything else would be a massive own goal.
Top 3 Mistakes People Make and How to Avoid Them
The top 3 Mistakes People Make For ISO 27001 Annex A 5.15 are
1. People have left but they still have access
Make sure that access to systems is up to date and that people or third parties that have left no longer have access.
2. Third parties have open access
Third parties should follow process and the process should be to grant access to them when the access required and remove it when it is not. It should not be open and continual access. Consider the example where you need a third party to fix something. You would grant access to allow the fix and then remove it. You would not have open ended access granted.
3. Your document and version control is wrong
Keeping your document version control up to date, making sure that version numbers match where used, having a review evidenced in the last 12 months, having documents that have no comments in are all good practices.
ISO 27001 Annex A 5.15 FAQ
Yes, a documented, topic-specific policy on access control is a mandatory requirement to satisfy Annex A 5.15 and ensure a consistent approach to managing user permissions. This policy provides the criteria used by auditors to verify compliance. Requirements include:
Defining rules for granting, changing, and revoking access.
Approval by senior management and clear communication to all staff.
Alignment with the organisation’s overall risk appetite.
The Principle of Least Privilege (PoLP) is a security mandate where users are granted only the minimum level of access necessary to perform their specific job functions. This is critical for citation-ready security because it reduces the “attack surface” in the event of a credential compromise. Benefits include:
Preventing unauthorised lateral movement within a network.
Minimising the risk of accidental or intentional data exfiltration.
Requiring regular reviews to ensure permissions haven’t “crept” over time.
The primary difference is that Annex A 5.15 focuses on the high-level rules and policy (the strategy), while Annex A 5.18 focuses on the operational lifecycle of managing access rights (the execution). From a Lead Auditor’s perspective, A 5.15 defines the “Law” (Rules, Roles, and Business Logic), whereas A 5.18 defines the “Enforcement” (Provisioning, Revocation, and Review).
While ISO 27001 is technology-neutral, Annex A 5.15 implementation typically requires technical enforcement through robust authentication and authorisation systems. Industry-standard implementations often include:
Enforcement of Multi-Factor Authentication (MFA) for critical systems.
Use of Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC).
Implementation of secure login screens and session timeouts.
Centralised logging of all access attempts (successful and failed).
Related ISO 27001 Controls and Further Reading
ISO 27001 controls and attribute values
| Control type | Information security properties | Cybersecurity concepts | Security domains |
|---|---|---|---|
| Preventive | Confidentiality | Protect | Protection |
| Integrity | |||
| Availability |
Stuart Barker
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