Access control


Access control

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It is a reality that the cyber security landscape is rapidly changing everyday. New threats emerge constantly and what was true 5 years ago might not be true today. In this reality, it is important to re-skill ourselves constantly.

Living in a hyper connected world, we are constantly signing into systems to access different types of information. Unauthorized individuals should never be able to access our resources.  How can this be done? By the very basic and fundamental concept in Information security – ‘access control’. 

What is Access control and what are the different types?

Access control ensures that only authorized individuals can access appropriate resources. Physical access control ensures that physical resources like specific rooms, buildings are accessed by appropriate people.Logical access control ensures that resources like networks, files are accessed by appropriate people. 

We observe the principles of ‘access control’ all around us unknowingly. When we share a post on social media platform, we set the permission to ‘public’ or ‘private’ or ‘Friends’ as the case may be. This makes sure that the post is visible only to necessary people and not all.

The simple example of checking email can also be mentioned here.  The correct combination of username and password authenticates the user to access his resources (email, in this case).

The different stages of access control are:


2. Authentication

3. Authorization

4. Accountability

‘Identification’ is done by providing the user with a unique id number, username or account number. ‘Authentication’ is done by providing the password or personal identification number. This correct combination of username and password reiterates the fact that the user is in fact “who he claims to be”. Once the user has been authenticated, the user next has to be authorized to access the resource. The ‘access control matrix’ is checked to make sure that if the user is the “person” authorized to access the requested resource. This is “authorization”. Finally the user is “accountable” for all the actions taken. To ensure accountability, user’s login information and subsequent actions are noted. 

Now that we have seen what is meant by ‘access control’ – we see the different access control models. There are three main types of access control models and they are discretionary access control, mandatory access control and role based access control. Every organization has different business objectives. The type of access control to be implemented is entirely dependent on its objectives as well the culture of the organization.

Discretionary access control:

Before we discuss the different access controls, we see what is meant by a “subject” and “object”. The “subject” is the one that is making the request for the resource and the “object” is the resource itself. In discretionary access control model, he who creates the information is the “owner”. The “owner” can decide who can access which data. Recall, that this is authorization. This is normally implemented by “access control lists” or ACLs. ACLs are specified by the system administrator and enforced by the operating system. The majority of the operating systems such as Windows, Linux and Macintosh systems are DAC based.

Mandatory Access Control:

The ‘mandatory access control’ is much more structured and organized than the DAC. In this type of access control, the operating system has the final say on who can access which resource. Users have security clearance (secret, top secret, confidential) and data is also classified in a similar way. The clearance and classification are stored as ‘security labels’.  When a user makes a request for a resource, it is dependent on the clearance of the individual, the classification of the data and the security policy of the system. This is enforced by the security officer and implemented by the operating system. This type of access control is used where security is of utmost importance. Normal DAC systems will not be suitable when the need is to classify data of special security clearance. We need MAC systems with special operating systems to enforce the rules.

Role based Access Control:

Role based access control or RBAC is also known as ‘non-discretionary access control’. In Role based access control, access to a particular resource is governed by the “role” an employee is mapped to. This type of access control is tougher to configure as the organizational policies have to be translated to roles. For example, an employee in “HR” does not need access to resources in “payroll”. RBAC is easy to configure when the employee turnover is high. When “Sam” from “Finance” leaves the organization and “Wendy” joins, “Wendy” is just mapped to “Finance” and she takes the same roles and responsibilities as the previous employee. There is no additional configuration needed here.

Access control is the basis of many topics and the RBAC model forms the basis of many identity management solutions.

We saw a very small portion of a fundamental concept in Information security. Join me as I uncover more!


Harris, S. All in one CISSP. In S. Harris.

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