Principle of Least Privilege - secuguru/security-terms GitHub Wiki

The Principle of Least Privilege (PoLP) is a fundamental security concept that involves granting users, applications, and processes the minimum level of access required to perform their tasks. By limiting privileges, PoLP reduces the attack surface and minimizes the potential impact of security vulnerabilities.

1. Key Features of PoLP

  • Minimal Access: Assign only the permissions and privileges necessary for the user or process to complete their specific job.
  • Scoped Access: Ensure that permissions are restricted to the necessary resources and operations.
  • Temporary Access: Grant elevated privileges only when required and remove them when they are no longer needed.

2. Importance of PoLP

  • Reduces Attack Surface: Limiting privileges prevents attackers from exploiting unnecessary permissions or accessing sensitive systems.
  • Mitigates Impact of Exploits: If a vulnerability is exploited, the damage is contained because the compromised process or user account lacks elevated privileges.
  • Prevents Lateral Movement: Attackers have fewer opportunities to escalate privileges or move across systems.
  • Compliance: Many regulations (e.g., GDPR, HIPAA, PCI DSS) require adherence to PoLP for protecting sensitive data.

3. Example: Running Internet Explorer with Administrator SID Disabled

  • Scenario: Running Internet Explorer (or any application) with the Administrator Security Identifier (SID) disabled ensures that even if the application is compromised (e.g., through a buffer overflow exploit), the attacker cannot perform administrative actions on the system.
  • How It Works:
    • By removing administrative privileges from the process token, the browser operates with reduced permissions.
    • Exploits cannot execute privileged actions like modifying system settings or accessing sensitive files.
  • Impact: Attackers must rely on privilege escalation techniques, significantly increasing the complexity of their attacks.

4. Common Implementations of PoLP

  • Users:
    • Users should not operate with administrative privileges for everyday tasks.
    • Example: Developers should use standard accounts for browsing the internet and reserve administrative accounts for specific tasks like software installations.
  • Applications:
    • Applications should run with limited permissions.
    • Example: A web server only needs access to serve files and log activity—it doesn’t require access to system configuration files.
  • Processes:
    • Processes should drop unnecessary privileges as soon as they complete tasks requiring elevated permissions.
    • Example: The sudo command in Linux grants temporary elevated privileges and reverts to normal privileges afterward.
  • Network Access:
    • Services and devices should only have access to the systems and networks they need.
    • Example: A database server should not have direct internet access.

5. Techniques to Enforce PoLP

  • Role-Based Access Control (RBAC):
    • Assign permissions based on roles rather than individual users, ensuring that roles are scoped to the least privilege.
  • Just-In-Time Access:
    • Provide temporary elevated privileges only when required (e.g., privilege elevation tools like sudo).
  • Network Segmentation:
    • Restrict access to sensitive systems and networks based on the principle of least privilege.
  • Application Sandboxing:
    • Run applications in isolated environments with restricted permissions.
  • Process Token Restrictions:
    • Modify process tokens to disable specific privileges (as in the Internet Explorer example).

6. Challenges in Implementing PoLP

  • Balancing Usability and Security:
    • Over-restricting access can frustrate users and hinder productivity.
  • Privilege Creep:
    • Over time, users or processes may accumulate unnecessary privileges due to role changes or lax permissions management.
  • Complexity in Large Environments:
    • Managing least privilege in environments with numerous users, systems, and applications requires robust tools and processes.

7. PoLP in Cloud and Modern Environments

  • Service Accounts:
    • Assign specific, minimal permissions to cloud service accounts.
    • Example: In AWS, use IAM roles with tightly scoped permissions.
  • Containers:
    • Run containers with non-root users and restrict access to the host system.
  • Zero Trust Architecture:
    • Apply PoLP at all levels, requiring continuous validation of users and devices for every access request.

8. Summary

Aspect Details
Definition Granting only the minimum necessary permissions to users, processes, and applications.
Example Running Internet Explorer with the Administrator SID disabled in its process token.
Benefits Reduces attack surface, mitigates exploits, prevents lateral movement.
Implementation Role-Based Access Control, Just-In-Time Access, Sandboxing, and token restrictions.
Challenges Balancing usability and security, managing privilege creep in large systems.
Modern Use Cases Cloud IAM roles, container isolation, and Zero Trust architecture.

By enforcing PoLP, organizations can significantly enhance security while limiting the impact of attacks and ensuring compliance with regulatory requirements. Combining PoLP with other security measures, such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR), further strengthens defenses.