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Allowlisting: What is it?

In the ever-evolving landscape of cybersecurity, it is essential to have effective measures in place to protect computer systems and networks from malicious activities. One such measure is allowlisting, also known as whitelisting.

Allowlisting is a proactive security approach that focuses on granting access only to known, trusted entities while denying access to everything else. In this article, we will explore what allowlisting is, how it works, its benefits, and best practices for implementing it.

What is Allowlisting?

Allowlisting, also referred to as whitelisting, is a security mechanism that permits only pre-approved entities, such as applications, processes, IP addresses, or users, to access a system or network. It essentially creates a trusted list of authorized entities that are allowed to perform specific actions or access specific resources. Any entity not explicitly included in the allowlist is automatically denied access or execution.

What is Blocklisting?

Blocklisting, on the other hand, is the opposite of allowlisting. It involves creating a list of known malicious entities or behaviors that are explicitly blocked or denied access. Blocklisting is reactive in nature, as it identifies and blocks threats based on known patterns or signatures. However, it may not be effective against new or unknown threats, as it relies on a database of known malicious entities.

Allowlisting vs. Blocklisting

Allowlisting and blocklisting are two different approaches to managing system or network access. Allowlisting focuses on allowing only trusted entities, while blocklisting focuses on blocking known malicious entities. Allowlisting provides a more proactive and restrictive approach by allowing access to a specific set of entities, while blocklisting relies on a blacklist that contains known threats.

Different Types of Allowlisting

There are various types of allowlisting, each serving different purposes and levels of granularity:

  1. Application Allowlisting: This type of allowlisting grants access only to approved applications or executables. It ensures that only authorized software can run on a system, reducing the risk of malware infections.

  2. IP Address Allowlisting: IP address allowlisting restricts access to a system or network based on approved IP addresses. This approach is commonly used to limit access to specific geographical regions or trusted networks.

  3. User Allowlisting: User allowlisting controls access to resources based on approved user accounts. It ensures that only authorized users can access sensitive data or perform specific actions.

How Allowlisting Works

Allowlisting works by creating a predefined list of trusted entities. When a request for access or execution is made, the system or network checks whether the entity is included in the allowlist. If it matches an entry in the allowlist, the request is granted. Otherwise, the request is denied. This approach provides a strong security barrier by default, as any unrecognized or unauthorized entity is automatically blocked.

Why Do We Need Allowlisting?

Allowlisting offers several advantages over other security measures:

  1. Enhanced Security: By allowing access only to trusted entities, allowlisting reduces the attack surface and minimizes the risk of unauthorized access or malware infections.

  2. Prevention of Zero-Day Attacks: Zero-day attacks are vulnerabilities that are exploited by cybercriminals before they are discovered by security experts. Allowlisting can effectively mitigate these attacks by blocking any unauthorized entity attempting to exploit a vulnerability.

  3. Control Over Software and Processes: Allowlisting allows organizations to have granular control over what software and processes are allowed to run on their systems, ensuring compliance and preventing the execution of unauthorized or malicious software.

Allowlisting Best Practices

To ensure the effectiveness of allowlisting, it is important to follow these best practices:

  1. Regularly Update the Allowlist: Keep the allowlist up to date by adding newly approved entities and removing outdated or unused ones. Regularly review and revise the allowlist to adapt to changes in the system or network.

  2. Implement Multiple Layers of Allowlisting: Combine different types of allowlisting (e.g., application, IP address, user) to create multiple layers of defense, providing a more robust security posture.

  3. Test and Validate Allowlist Entries: Before adding entities to the allowlist, thoroughly test and validate their legitimacy to avoid unintentionally granting access to malicious or unauthorized entities.

How to Start Allowlisting

To start allowlisting in your organization, follow these steps:

  1. Identify Critical Resources: Determine the critical systems, networks, and data that require strict access control.

  2. Create an Allowlist Policy: Define the rules and criteria for adding entities to the allowlist, such as approved applications, IP addresses, or user accounts.

  3. Deploy Allowlisting Solutions: Implement allowlisting solutions or tools that automate the process of managing and enforcing the allowlist.

  4. Educate and Train Employees: Provide training to employees on the importance of allowlisting and how to follow best practices to ensure its effectiveness.


Allowlisting is a proactive security approach that allows access only to known, trusted entities while denying access to everything else. By implementing allowlisting, organizations can significantly enhance their security posture, reduce the risk of unauthorized access or malware infections, and gain better control over their systems and networks. By following best practices and starting with a well-defined allowlist policy, organizations can effectively implement and maintain a robust allowlisting strategy.

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