The principle of least privilege (PoLP), also known as the principle of minimal privilege or the principle of least authority, is an information security concept. It states that any user, device, workload, or process should only have the bare minimum privileges it needs to perform its intended function.
The word privilege in this context refers to system rights or data access. For instance, it determines which users can access a particular file or which devices can access a specific network. It is also used to define what users can do on a system. For example, some users may only be able to execute particular functions, while others may be able to do more such as restart the application or apply updates.
Information security practice typically categorizes accounts as either privileged or non-privileged. Privileged accounts can refer to user accounts or system accounts with greater access to system functions or stored data. For example, a system administrator that can apply updates, add users, and restart an application is a privileged account. Similarly, an application's service account that can access confidential information in a database, such as customer credit card details, is another example of a privileged account.
The primary objective of the principle of least privilege is to enhance the security of an application, network, or technology environment. As threat actors follow the path of least resistance when trying to obtain unauthorized access to a system, PoLP fortifies systems by reducing the number of potential access points. Similarly, it protects an organization from downtime or data breaches due to user error.
The following analogy illustrates the principle of least privilege in both scenarios. Consider a bank with general staff and a bank manager. Applying the principle of least privilege, the manager needs access to the safe. However, the other staff members do not. As a result, the manager is the only individual with the keys. If a bank robber enters a bank where everyone has access to the safe, robbing that bank would be far easier than another bank where only the manager has the keys. Similarly, if every staff member has keys to the safe, the likelihood of them falling into the wrong hands increases exponentially.
As illustrated in the analogy, the principle of least privilege reduces the potential attack surface. The same rule applies to information security. The fewer people with privileged access to a system or data, the less risk to the system from an attack or user error. In addition to reducing the attack surface, PoLP limits the potential damage and improves the management and maintainability of a technology environment. For instance, it provides data security and audit capabilities, improving compliance and reporting.
Managing the information security of an environment by implementing the principle of least privilege is not an event but a process. As a result, system administrators need to monitor their environment and continuously ensure that PoLP is enforced in the strictest possible terms.
The following terms and concepts relate to PoLP and define particular scenarios that relate to the implementation of an effective PoLP strategy.
Privilege creep: Privilege creep is the gradual accumulation of access rights. In many instances, the additional access rights are beyond what the users need to perform their duties. Privilege creep often occurs when individuals move departments within an organization. For instance, a user transferred from Finance to HR is given access to the HR system, but their access to finance is not revoked. As a result, the principle of least privilege is not being applied correctly as the user no longer needs access to finance to do their job.
Privilege bracketing: Privilege bracketing is an information security concept where a standard user is provided with elevated privileges for a brief moment. An excellent example of this is the Sudo command in Linux or the User Account Control (UAC) function in Windows. In both instances, when a user wants to install software or run a command that needs access to secure areas of the operating system, they are prompted to enter an administrative username and password. Once the privileged execution completes, the user no longer has elevated access. Privilege separation: The concept of privilege separation refers to a technique where the functionality of a system is divided into separate parts. The system then assigns access to each part to a different set of privileged users. For example, some users can load payments in many banking systems, and other users can release them. The users that can load payments do not have release privileges. Likewise, the users that can release payments do not have the privileges to load them. This segregation of duties reduces the risk of fraud or embezzlement as two separate individuals are needed to make one payment.
Privilege escalation: Privilege escalation is a form of cyberattack where an attacker gains unauthorized access to elevated rights or privileges. For instance, an application error may provide a regular user with access to administrative functions. Another example of privilege escalation is an external attacker exploiting a known system vulnerability to execute commands as administrator.
Zero Trust is an information security concept that states that an organization should deem any activity in its technology environment as untrusted. The model places data at its core and considers any workload, user, device, or network interacting with it as suspicious. Taking this prudent approach, the model states that organizations should authenticate and authorize every action and segment their environments. Finally, Zero Trust recommends that all data, whether in transit or at rest, should be protected with encryption.
The principle of least privilege aligns with the concept of Zero Trust. However, the two are distinct concepts. You can implement PoLP without Zero Trust. For instance, you could limit access to a system or data based on user roles and not implement network segmentation or encryption. Conversely, it would be impossible to implement Zero Trust without enforcing the principle of least privilege. As the model deems any action as untrusted, logic dictates that you must limit access to systems or data. Furthermore, administrators should only grant access to users, devices, networks, or workloads that need it to perform an authorized function.
Privileged Access Management (PAM) is an information security mechanism that safeguards identities with special access or capabilities beyond regular users. It deals with the security processes and technologies required to protect privileged accounts. A PAM solution enables and enforces the principle of least privilege. However, implementing a Privileged Access Management solution does not mean you have implemented PoLP. It is only one of the components of an overarching PoLP strategy. While PAM provides administrators with the functionality, automation, and reporting they need to manage privileged accounts, it does not limit access to systems and data. You would need to use other technologies or built-in system capabilities to restrict access.
Just-in-time access is a concept that stems from Identity and Access Management (IAM). Its approach is to reduce the risk of 'standing privileges.' For instance, when an organization grants a user administrator access, it gives the individual elevated rights to systems and data. Typically, it statically assigns those elevated rights that remain in perpetuity. Just-in-time access is a solution that grants a user elevated privileges when they need to perform an administrative function and then automatically removes it once the individual completes the action. The concept of Just-in-time aligns with privilege bracketing. It is dependent on PoLP as you cannot implement Just-in-time if you do not have the principle of least privilege in place.
To illustrate the principle of least privilege further, let's use another analogy. In this example, we will use the scenario of a passenger aircraft. On the aircraft, there are passengers and crew. As the flight crew needs to manage the plane's functions, including flying it from point A to point B, they have the elevated privileges required to perform their duties. For instance, the captain and pilot can access the flight controls, but the flight attendants and passengers cannot. Likewise, the flight attendants have access to the galley to prepare meals and beverages, while the passengers are confined to the cabin. This scenario illustrates the implementation of an effective PoLP strategy. It defines and restricts each individual’s role on the aircraft, limiting them to the areas and capabilities each one needs to perform their duties.
The principle of least privilege is a concept that is only as effective as its implementation. Therefore, organizations should consider the following best practices:
Conduct an audit: Before implementing PoLP, understanding the current level of access across all your systems is vital. Conducting a privilege audit can help you identify users with privileged access and if they need it to perform their duties.
Enforce the separation of privileges: Enforcing the separation of privileges will allow you to tighten security controls and identify areas where restricted access is required.
Start all accounts with the least privilege: Create all new accounts with no privileges and only add them when needed. Avoid privilege creep by removing access when users change job roles.
Leverage Just-in-time privileges: Leverage Just-in-time privilege solutions to strengthen the security of your technology environment. There are very few instances where an administrator will need perpetual access.
Audit access: Once you have implemented the principle of least privilege, it is vital that you continuously monitor your technology environment. Where possible, enable auditing so that you can trace individual accounts.
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