Principle of Least Privilege

Introduction

Understanding the principle of least privilege is essential for any IT professional. It is a fundamental security concept that can be applied to applications and infrastructure with an aim to improve your security posture and reduce the risk of a security breach. It can be difficult to strike a balance between protecting your data without causing friction for users, but understanding the principle of least privilege can help you achieve this.

In this blog, I will be discussing the principle of least privilege and how it can be applied to applications and infrastructure to help secure your products and services.

Understanding the Principle of Least Privilege

The Principle of least privilege is a security concept that aims to reduce the risk of a security breach by limiting user permissions to the bare minimum required to perform their job. This can also be referred to as the principle of least authority or the principle of minimal privilege, and acts as a safeguard to protect against unauthorized access and misuse of privileges.

Imagine you are a bank manager, and you have a safe in your office that contains all of the money for the bank. You would not give the key to the safe to every employee in the bank. Instead, you would only give the key to the safe to a select few people who need access to it. This is an example of the principle of least privilege in action.

Importance of the Principle of Least Privilege

Ensuring your organization follows the principle of least privilege is essential for protecting your data and reducing the risk of a security breach. This will not prevent a security breach from happening, but will help limit the blast radius and potential damage caused by an incident.

One of the primary benefits of least privilege is it’s ability to minimise the attack surface. By restricting access rights, organizations reduce the potential entry points that a malicious actor could exploit, and in the event of a compromise, the attacker will be contained to a smaller area of the network, meaning they will have less access to other systems and data.

Adhering to the principle of least privilege is often a requirement for compliance with regulations such as the General Data Protection Regulation (GDPR) and the Payment Card Industry Data Security Standard (PCI DSS). These regulations require you to protect your data and only give access to those who need it. Failure to comply with these regulations can result in significant fines and reputational damage.

There are many stories of the intern who nuked the production database or the company who had to shut down after being held to ransom because they didn’t follow basic security practices. If these companies had followed the principle of least privilege, these incidents could have been avoided as the intern should not have had access to the production database, and the ransomware would have been contained to a smaller area of the network.

Edward Snowden and the NSA

In 2013, Edward Snowden, a former CIA employee, leaked classified information from the National Security Agency (NSA) to the press. This data revealed the NSA’s global surveillance program, which was collecting data from millions of people worldwide. Snowden did not need to have access to these resources to perform his job, but he was able to access, export and leak this information because he had far more privileges than required.

In this case, the NSA failed to implement the principle of least privilege, which contributed towards a significant security breach of classified information and reputational damage. Organizations should learn from this, especially those who handle sensitive data.

Applying the Principle of Least Privilege

Now that we understand what the principle of least privilege is and why it is important, let’s look at how we can apply it to applications and infrastructure.

Applications

Implementing least privilege requires you to understand the permissions required by each user and only grant them the permissions they need to perform their job.

This can be achieved by following these three steps:

1. User Roles and Permissions

   Define distinct roles within your application, each with specific permissions based on the users’ day-to-day tasks and responsibilities. Users should only be assigned the role that aligns with their job function. For example, a customer service representative shouldn’t have the same level of access as a system administrator.

2. Regular Audits

   User permissions should be reviewed regularly to ensure they are still required. People change roles or leave the company, and sometimes permissions granted previously are no longer necessary. Regular audits will help you identify these permissions and remove them.

3. Least Privilege by Default

   When creating new roles, you should always start with the least privilege and only add permissions when required. This will help you avoid granting unnecessary permissions and reduce the risk of a security breach.

Infrastructure

Least privilege in your infrastructure works in a similar way to applications. A malicious actor could exploit a vulnerability in your infrastructure to gain access to your network, so it’s essential to ensure that your infrastructure is not over-privileged. This can be achieved by following these three steps:

1. Network Segmentation

   Network segmentation is the process of dividing a network into smaller subnetworks. This can be done by creating separate VPCs, VLANs or using firewalls to separate different parts of your network. This will help you limit the impact of a security breach by containing it to a smaller area of your network. If a service does not need to talk to a database, then the network policies should be configured to prevent this communication.

2. Restricted Service Account Permissions

   Just like user access, the permissions provided to your infrastructure should be restricted as much as possible. Lambda functions should only be able to interact with the services and specific resources that they require. This will help reduce the risk of an attacker moving laterally through your network.

3. Least Privilege by Default

   When creating new services, you should always start with the least privilege and only add permissions when required. This will help you avoid granting unnecessary permissions and reduce the risk of a security breach. Yes, this can and will be annoying and frustrating at times, but it’s key to securing your environment.

Closing thoughts

The principle of least privilege is a fundamental security concept that can be applied to applications and infrastructure to improve your security posture and reduce the risk of a security breach. It can be difficult to strike a balance between protecting your data without causing friction for users, but understanding the principle of least privilege can help you achieve this. I hope this blog has helped you understand the principle of least privilege and how it can be applied to applications and infrastructure, and I encourage you to implement it in your organisation.