Operational resilience

February 25, 2020

In the UK, the National Cyber Security Centre (NCSC) runs an information assurance scheme called Cyber Essentials.  Our blog post series looks at each of the framework’s five focus areas and offers practical hints and tips on security requirements and value to organisations wishing to follow its advice.

This post is the fourth in the Cyber Essentials series, you can read the earlier posts here, here and here.  In this post, we look at the importance of controlling access to your critical business information and business services. Access control is the third on NCSC’s list of five Cyber Essentials security controls, and whilst its importance is not as obvious as some of the others, once you look at the detail, you’ll see why access management is crucial in securing your business.

What is Access Control?

Controlling access to data and services refers to limiting users to only those information assets or services they need to do their job. If someone in your sales team has no need to access your organisation’s HR files or secret plans for a new product, you can apply special permissions to ensure those members of staff can only see the data they need – sales and commercial information. The rest of your company data is blocked.

Access control, however, is about more than just blocking access to information.  It is also a consideration for threat management, both from internal and external attackers who may seek to exploit weaknesses in permissions for their own nefarious gains. You can reduce the extent an attacker can move through your environment by ensuring all accounts (and hence compromised accounts) only have the access they need, so attackers are limited in their ability to jump laterally around the business looking for data to steal.

You should also consider a granular approach to access control for administrators too, since they have superuser powers (and superuser access) to your business.  This means that any breach of those accounts could be even more devastating than a normal user account breach.

Ideally, we’d recommend that you decide on required permissions and privileges for each type of user and administration account to do their jobs; administrative roles should be a priority and only have administrative role functionality, for example, if you have a service desk technician who resets user passwords, they should not have permissions and privileges to delete event logs, backups or add new users to groups.

Separation of duties

There should be at least two kinds of accounts within your business, but there may be more depending on how you segment workforce responsibilities. There are some valid reasons for having multiple accounts per user, but it’s important that you don’t overdo it as it adds an administrative overhead.  Use common sense and make risk your priority in any decision making.

Why would staff have more than one account?

The simplest example of using multiple accounts in practice is when you give system administrators one account for their administrative duties and one for normal user work. By using the normal user account for general business activities such as browsing the Internet or sending company emails, any compromise of that account limits the harm the hacker can cause to the permissions of the normal user. If an administrator account is breached, this is a lot worse. By prohibiting the normal user activities from the administrator account, you can stop the system administrators from being phished or hacked from outside the organisation: most hacks begin with phishing attacks delivered to the victim over email.

Some businesses also separate the duties of other critical roles, not just the system administrator/normal user divide. For example, an organisation concerned that it’s bank accounts might be compromised might have a special account that can only access their bank accounts and payment services. This approach limits the attack surface and closes the email and open browser access, restricting it to the online website provided by the bank.

Permission Creep

The primary value of access control to your organisation is implementing a need-to-know model that limits the harm user accounts are exposed to if they go rogue or are compromised.  You will need to consider more than the technology elements of access control to fully implement a measure that protects the business, since assurance processes need to be used to make sure the technical position you expect is maintained over time.

If a user changes roles within the business, new permissions are added to their profile to allow them to do their job. Organisations sometimes forget to remove old permissions that are no longer required for that user, and over time users accumulate more permissions than they need to do their job. This accumulation poses a greater risk for the business as a breached account opens access to a lot more of the business’s data than it should.

If your organisation already audits permissions, we’d recommend that you also review active user accounts. In some cases, this is the only way of discovering certain users you thought had been deactivated are not suspended. The risk of not checking this is the scenario where a user leaves the organisation and their account is left active, the user could log back into the business later and download data they are no longer permitted to see. Furthermore, if that account was breached, and there was no active user to notice odd behaviour, an attacker may have free reign over the business for an indefinite amount of time.

Next steps towards Cyber Essentials compliance

In this post, we looked at the Cyber Essentials requirement to control access to your data and services.

In future posts, we will look at the remaining two baseline technical controls and explain how each one can play a vital role in determining an organisation’s security posture.

Cyber Essentials Compliance Guide


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