Discretionary Access Control
Discretionary access control (DAC) is a type of access control where the owner of a resource determines who can access it and what permissions they have. It is a fundamental concept within information security, a broad category of practices and technologies designed to protect information from unauthorized access, use, disclosure, disruption, modification, or destruction. DAC offers a flexible approach, allowing owners to grant or revoke specific access rights at their discretion, often based on the identity of a subject (user or process) or the groups to which they belong.
History and Origin
The concept of discretionary access control emerged with the development of multi-user operating system environments, where multiple users needed to share computing resources while maintaining separation and control over their private files and data. Early discussions and models for access control, including those that laid the groundwork for DAC, date back to the 1960s and 1970s. Key academic works by Lampson, Graham-Denning, and others helped formalize these concepts. The notion of an "owner" having the authority to grant permissions to others became a cornerstone of these systems. The U.S. National Institute of Standards and Technology (NIST) defines discretionary access control as an access control policy that allows a subject (user) with granted access to information to, among other things, pass that information to other subjects or objects, or change the rules governing access control for resources they control.9 This ability for resource owners to manage access distinguishes DAC. Early computer security models, such as those described in academic papers, often detailed how such controls could be implemented and the implications of this discretionary power.8
Key Takeaways
- Discretionary access control (DAC) allows resource owners to define and manage access rights for their own resources.
- It provides flexibility, enabling granular control over individual files, folders, or other objects.
- DAC is commonly implemented through access control lists (ACLs) or permission bits in file systems.
- The effectiveness of DAC heavily relies on the diligence and judgment of the resource owners in setting appropriate security policies.
- While flexible, DAC can lead to inconsistent security postures across an organization if not managed alongside broader organizational information governance policies.
Interpreting Discretionary Access Control
Discretionary access control is interpreted and applied as a core mechanism for protecting digital assets. When a system employs DAC, it means that the individual or entity that "owns" a piece of data or a system resource has the authority to decide who can interact with that resource and in what manner. For instance, the creator of a document might grant "read-only" access to one colleague and "read-write" access to another.
The interpretation also extends to the principle of least privilege, which suggests that users should only be granted the minimum permissions necessary to perform their tasks. While DAC provides the tools to implement this, it is up to the resource owner or system administrator to enforce it. The system's ability to enforce DAC means that every request for resource access is checked against the defined permissions before authorization is granted.
Hypothetical Example
Consider a financial analyst, Sarah, who creates a highly sensitive spreadsheet containing quarterly earnings projections. Her computer's operating system uses discretionary access control for its files.
- Creation and Default: When Sarah creates the spreadsheet, she is automatically designated as its owner. By default, the system might grant her full control (read, write, execute) and perhaps read-only access to a specific group she belongs to (e.g., "Finance Department," which includes her manager).
- Sharing with Specific Colleagues: Sarah needs a colleague, Alex, to review and edit the projections. Using the file properties or sharing settings, she explicitly grants Alex "read and write" permissions to only this specific spreadsheet.
- Sharing with Auditors: A team of external auditors needs to view the final projections but should not be able to modify them. Sarah then grants the "Auditors" group "read-only" access to the file.
- Revoking Access: After the earnings report is published, Sarah might revoke all external access to the file, ensuring only she and her immediate manager retain permissions, thereby enhancing data security.
In this scenario, Sarah, as the owner, exercises discretion over who can access her specific resource, illustrating the core functionality of discretionary access control. The integrity and confidentiality of the financial data are maintained through her explicit management of access rights.
Practical Applications
Discretionary access control is widely applied across various domains, particularly in environments where granular control over individual resources is critical. In finance, DAC plays a vital role in safeguarding sensitive information. For instance:
- Financial Data Management: Financial institutions use DAC to control access to client portfolios, transaction histories, and proprietary trading algorithms. An investment advisor might have full control over their client's specific financial records, while a back-office staff member might only have read-only access for reporting purposes.
- Regulatory Compliance: Regulators, such as the U.S. Securities and Exchange Commission (SEC), emphasize the importance of safeguarding customer information.7 Regulations like SEC Regulation S-P require financial institutions to adopt policies and procedures for the protection of customer records and information.6 This often translates into implementing stringent access control mechanisms, where DAC components ensure that sensitive customer data is accessible only to authorized personnel. DAC contributes to meeting the availability and integrity objectives of information security by controlling who can modify or delete data.
- Cloud Computing and Collaboration: In cloud environments, DAC allows users to share documents and folders with specific individuals or groups, granting varying levels of authorization, from viewing to editing. This flexibility is essential for collaborative financial analysis and reporting while maintaining control over who can modify shared datasets.
Limitations and Criticisms
While discretionary access control offers flexibility, it also presents several limitations and criticisms:
- Reliance on User Discretion: The primary drawback of DAC is its heavy reliance on the individual users or owners to correctly manage their resource permissions. If an owner misconfigures permissions, either accidentally or maliciously, it can lead to unauthorized access to sensitive data. For example, leaving a highly confidential financial report openly accessible can compromise data security for the entire organization.
- Potential for Inconsistent Security: In large organizations, different owners setting their own access rules can result in inconsistent security policies across the enterprise. This lack of uniformity can create security loopholes and make overall security management complex and error-prone.
- Propagation of Permissions: DAC systems can allow a subject with certain access permissions to pass those permissions (perhaps indirectly) on to other subjects.5 This can lead to an unintended propagation of access rights, making it difficult to trace who has access to what, a concept sometimes referred to as the "Trojan Horse problem."
- Vulnerability to Insider Threats: Because DAC grants significant power to resource owners, it can be susceptible to insider threats where an authorized user abuses their legitimate access rights. Failures in access control, often stemming from misconfigurations or lack of proper authentication, are a leading cause of data breaches.4 The Open Web Application Security Project (OWASP) lists "Broken Access Control" as a critical security vulnerability, noting that such flaws can lead to unauthorized information disclosure, modification, or destruction of data.2, 3
Discretionary Access Control vs. Role-Based Access Control
Discretionary access control (DAC) and role-based access control (RBAC) are two distinct approaches to managing access rights, often contrasted due to their different philosophies.
| Feature | Discretionary Access Control (DAC) | Role-Based Access Control (RBAC) |
|---|---|---|
| Control Authority | Resource owner | Central authority (e.g., system administrator) |
| Granularity | Very fine-grained (individual files/objects) | Role-based (collections of permissions for specific job functions) |
| Flexibility | High, owners can change permissions at will | Moderate, changes require modification of roles or user assignments |
| Scalability | Can be complex to manage in large organizations | Highly scalable, easier to manage large user bases and permissions |
| Policy Enforcement | Decentralized, relies on owner discretion | Centralized, enforced through predefined roles |
| Common Use Cases | Personal files, collaborative documents, specific project folders | Enterprise applications, large corporate networks, regulatory compliance |
The primary point of confusion often lies in their respective levels of control. DAC empowers the individual, granting them the discretion to manage access to their owned resources. In contrast, RBAC centralizes control, assigning permissions based on a user's organizational role, independent of specific resource ownership. RBAC typically offers a more consistent and scalable solution for larger enterprises, ensuring that permissions align with predefined job functions rather than individual preferences.
FAQs
What is the main characteristic of discretionary access control?
The main characteristic of discretionary access control is that the owner of a resource or an authorized entity has the ability to grant or revoke access permissions for that resource at their own discretion.
Where is discretionary access control commonly used?
Discretionary access control is commonly used in operating systems and file systems, where users are typically the owners of the files and directories they create. It is also found in many cloud storage and collaboration platforms where users share content.
What are the risks associated with discretionary access control?
Risks associated with discretionary access control include inconsistent security policies due to varying owner diligence, the potential for unauthorized privilege escalation through misconfigurations, and challenges in maintaining overall security posture in large environments. These issues can lead to "Broken Access Control" vulnerabilities where attackers gain unauthorized access.1
How does discretionary access control relate to financial data?
In the context of financial data, discretionary access control is critical for maintaining the confidentiality and integrity of sensitive information. Financial professionals may use it to control who can view, edit, or delete specific client records, investment analyses, or proprietary data, helping to comply with data security regulations.
Is discretionary access control the only type of access control?
No, discretionary access control is not the only type. Other common models include mandatory access control (MAC), which enforces a system-wide policy regardless of resource ownership, and role-based access control (RBAC), which assigns permissions based on a user's defined role within an organization. Many systems employ a combination of these models for comprehensive security.