ISO 27002:2022, Control 5.15 – Access Control

General Guidance

Compliance with Control 5.15 involves adhering to what’s known as a ‘topic-specific’ approach to Access Control (more commonly known as an ‘issue-specific’ approach).

Topic-specific approaches encourage organisations to create Access Control policies that are tailored towards individual business functions, rather than adhering to a blanket Access Control policy that applies to data and resource access across the board.

Control 5.15 requires Access Control policies across all topic-specific areas to take the following 11 guidance points into consideration. Some of the below guidance points intersect with various other controls, which are listed for reference.

Organisations should consult these accompanying Controls on a case-by-case basis, for further information.

• Determine what entities require access to certain pieces of information and/or assets.
  
  

  Compliance – This is easily achieved by keeping an accurate record of job roles and data access requirements, that is in line with your organisational structure.

• The integrity and security of all relevant applications (linked with Control 8.2)
  
  

  Compliance – A formal risk assessment could be carried out to examine the security characteristics of individual applications.

• Physical (site) access controls (linked with Controls 7.2, 7.3 and 7.4)
  
  

  Compliance – Your organisation needs to be able to demonstrate that you have a robust set of building and room access controls, including managed entry systems, security perimeters and visitor procedures, where appropriate.

• A company-wide “need to know” principle, when it comes to information distribution, security and categorisation (linked with 5.10, 5.12 and 5.13)
  
  

  Compliance – Companies should adhere to strict best-practice policies that do not offer blanket access to data across an organisational chart.

• Ensure restrictions to privileged access rights (linked with 8.2)
  
  

  Compliance – Data access privileges above and beyond that of a standard user need to be closely monitored and audited.

• Adherence to any prevailing pieces of legislation, sector-specific regulatory guidelines or contractual obligations related to data access (linked with 5.31, 5.32, 5.33, 5.34 and 8.3)
  
  

  Compliance – Organisations tailor their own Access Control policies in accordance with any external obligations they have with regards to data, asset and resource access.

• Oversight of potential conflicts of duty
  
  

  Compliance – Policies should include controls that eliminate an individual’s ability to compromise a broader Access Control function, based on their own levels of access (i.e an employee who has the ability to request, authorise and implement changes to a network).

• The three main functions of an Access Control Policy – requests, authorisations and administration – should be addressed in isolation
  
  

  Compliance – Access Control policies need to acknowledge that whilst Access Control is a self-contained function, it’s made up of a number of individual steps that carry their own set of requirements on a topic-by-topic basis.

• Access requests should be conducted in a structured, formal manner (linked to 5.16 and 5.18)
  
  

  Compliance – Organisations should implement an authorisation process that requires formal, documented approval from an appropriate member of staff.

• Ongoing management of access rights (linked to 5.18)
  
  

  Compliance – Data integrity and security perimeters need to be maintained through a continual cycle of periodic audits, HR oversight (leavers etc.) and job-specific changes (e.g. departmental moves and role amendments).

• Maintaining adequate logs, and controlling access to them
  
  

  Compliance – Organisation should collect and store data on access events (e.g. file activity) alongside safeguarding against unauthorised access to security event logs, and operate with a comprehensive set of incident management procedures.

Guidance on Implementing Access Control Rules

As we’ve discussed, Access Control rules are granted to various entities (human and non-human) that exist on a given network, which in turn are given ‘roles’ that dictate their overall requirements.

As your organisation defines and enacts its own set of Access Control policies, 5.15 asks you to take the following 4 points into consideration:

1. Ensure consistency between the access right, and the kind of data it applies to.
2. Ensure consistency between the access right, and the physical security requirements of your organisation (perimeters etc).
3. Where your organisation operates under a distributed computing environment that includes multiple distinct networks or sets of resources (such as a cloud-based environment), access rights consider the implications of data contained across a broad range of network services.
4. Be mindful of the implications surrounding dynamic access controls (a granular method of access implemented by system administrators to a detailed set of variables).

Documentation and Defined Responsibilities

Control 5.15 is explicit in requiring organisations to preoccupy themselves with documentation and a structured list of responsibilities. ISO 27002 contains numerous similar requirements across its entire list of controls – here are the individual controls that are most relevant to 5.15:

Documentation

• 5.16
• 5.17
• 5.18
• 8.2
• 8.3
• 8.4
• 8.5
• 8.18

Responsibilities

• 5.2
• 5.17

Granularity

Control 5.15 gives organisations a significant amount of leeway when it comes to choosing the level of granularity contained within their Access Control rules.

ISO advises companies to exercise their own judgement on how detailed a given set of rules need to be on an employee-by-employee basis, and how many access variables are applied to any piece of data.

5.15 explicitly acknowledges that the more detailed a company’s Access Control policies are, the greater the cost and the more difficult the whole concept of Access Control becomes across multiple locations, network types and application variables.

Access Control as a concept, unless closely managed, can soon get out of hand. It is almost always a good idea to simplify Access Control rules to make them easier and more cost-effective to manage.

Changes From ISO 27002:2013

27002:2013/5.15 is an amalgamation of two similar controls in 27002:2013 – 9.1.1 (Access control policy) and 9.1.2 (Access to networks and network services).

In general, both 9.1.1 and 9.1.2 address the same underlying themes as 5.15 and broadly follow the same set of governance guidelines, with some subtle operational differences.

Both the 2022 and 2013 controls deal with administering access to information, assets and resources and operating along a “need to know” principle that treats corporate data as a commodity which needs to be closely managed and protected.

All of 27002:2013/9.1.1’s 11 governing guidelines run along the same general lines as is seen in 27002:2013/5.15, with the latter featuring a marginally greater emphasis on physical security and perimeter security.

Supporting guidance on Access Control implementation is broadly the same, however the 2022 control does a much better job of offering concise, practical guidance across its 4 implementation guidelines.

Changes in types of Access Controls from 9.1.1

5.15 acknowledges the different kinds of Access Control methods that have emerged over the last 9 years (MAC, DAC, ABAC), whereas 27002:2013/9.1.1 limits its guidance to RBAC – the most common method of commercial access control at that time.

Granularity

In conjunction with technological changes that offer organisations greater control over their data, neither of the 2013 controls contain any meaningful direction on how an organisation should approach granular access controls, whereas 27002:2013/5.15 gives organisations a significant amount of leeway.