Web Security

Allowlisting vs Blocklisting: Benefits and Challenges

July 2nd, 2024 | By Ejiro Thankgod | 12 min read

In cybersecurity, the strategic control of network access plays a pivotal role in safeguarding digital assets. Allowlisting vs. blocklisting emerge as two fundamental approaches in this endeavor, each offering distinct benefits and challenges. Allowlisting involves granting access only to pre-approved entities, promoting a proactive defense against potential threats. On the other hand, blocklisting aims to thwart known malicious entities swiftly, offering simplicity and quick response capabilities.

This exploration delves into the intricacies of allowlisting and blocklisting, dissecting their advantages and limitations.

As organizations grapple with the relentless surge of cyber threats, understanding the nuanced dynamics between these two methods becomes essential for establishing robust and adaptive security measures.

Importance of Allowlisting and Blocklisting in Cybersecurity

In the constant battle against cyber threats, allowlisting and blocklisting stand as essential tools in any cybersecurity arsenal. While seemingly opposites, they work together to create a layered defense, offering complementary benefits that significantly enhance overall security.


  • Reduced Attack Surface: By explicitly defining and approving only authorized entities, you shrink the potential entry points for threats, minimizing the damage they can inflict. This "trust-but-verify" approach offers proactive protection in a world teeming with unknown malware.

  • Simplified Management: Maintaining a whitelist of known good entities is often easier than keeping track of ever-evolving bad actors. This efficiency translates to faster response times and a reduced administrative burden.

  • Compliance Adherence: Many regulations require specific restrictions on data access or software usage. Allowlisting ensures automatic compliance, simplifies regulatory adherence, and reduces risk.


  • Proactive Threat Prevention: By actively blocking known malicious actors, spam, and harmful content, you prevent them from reaching your systems in the first place. This proactive approach stops threats before they can even attempt infiltration.

  • Reduced Damage Potential: Even the most robust defenses can be breached. Blocklists act as a secondary line of defense, mitigating the damage caused by successful attacks by restricting the attacker's movement within your network.

  • Improved Productivity and Control: Blocking unproductive websites and applications can enhance user focus and productivity. Additionally, content moderation becomes easier through targeted blocking, creating a safer and more controlled online environment.


Allowlisting, also known as whitelisting, employs the core concept of "zero trust" to block access by default, allowing only expressly approved sources to access an asset. Whitelisting can be used on any asset (network, endpoint, application, etc.) to grant particular access to any sort of source.

Consider your company's network to be a tightly secured entrance, with your admin serving as the diligent security guard in the front. Allowlisting works in the same way that security guards confirm employees with approved IDs. It maintains an exclusive list of accepted applicants, allowing only well-vetted personnel to enter. 

Allowlisting Use Cases

Allowlisting should be utilized when access can be clearly defined, such as for internal resources. Examples of effective allowlisting use cases are:

  • Email security program, allowlisting email addresses ensures proper email delivery from trusted senders.

  • IP address allowlisting in a firewall for branch offices

  • Web address allowlisting on a server to restrict the potential external connections for a susceptible asset.

  • Device Allowlisting MAC addresses and programs for network access and internal database access.

  • User allowlisting for an internal company application.

Benefits and Challenges of Allowlisting

Though blocklisting was formerly popular, the recent exponential surge in malware implies that it is no longer effective.

Allowlisting only enables a few programs to operate, effectively reducing the attack surface. Furthermore, creating an allowlist is much easier because the number of trusted programs is significantly lower than the number of distrusted ones. Allowlisting can help businesses adhere to tight regulatory compliance requirements.

Allowlisting has some drawbacks, despite its many advantages. Building an allowlist may appear simple, but one mistake might result in a backlog of help desk inquiries for the administrator. The inability to access important apps would hinder a variety of critical tasks. Furthermore, deciding which programs should be allowed to run is a time-consuming task.

As a result, administrators often implement extremely wide allowlisting policies. This mistaken faith might jeopardize the entire company. Another downside is that, whereas blocklisting can be partially automated with antivirus software, allowlisting requires human participation to function properly.


Blocklisting, also known as Blacklisting, is a security mechanism that prevents known dangerous people, IP addresses, websites, devices, or programs from accessing an organization's resources.

Many security systems have a blocklist as part of their anti-malware or attack-blocking features, which organizations can manually add to. Blocklisting does not adhere to the principles of zero trust because the default condition for access is to typically allow access until blocklisted.

Blocklisting is one of the oldest computer security techniques, and most antivirus software uses it to block harmful organizations.

The process of blocklisting applications is compiling a list of all the applications or executables that could constitute a hazard to the network, either through malware assaults or simply by interfering with productivity. Blocklisting might be viewed as a threat-centric technique.

Blocklisting Use Cases

When potential access sources are difficult to establish, such as with public resources, blacklisting is frequently the preferred option. Examples of effective blacklisting use cases are:

  • Email security software, email addresses that are known to convey spam or viruses are blacklisted.

  • In a firewall, IP addresses are blacklisted as the source of harmful assaults.

  • DNS server blacklists pornography websites and MAC addresses of known botnets.

  • Application blacklisting, like malware signatures in an antivirus program

  • User blacklisting of users who violated community rules in a discussion forum.

Benefits and Challenges of Blocklisting

The obvious advantage of blocklisting is its simplicity. Administrators can quickly disable known malicious applications while running everything else. This ensures that users have access to all of the applications they require, lowering the number of admin tickets raised or vital applications disabled. Blocklisting is an effective strategy for businesses looking to take a more liberal approach to application restrictions.

However, merely blocking anything that is distrusted, while simple and efficient, may not always be the best strategy. Every day, over 200,000 samples of malware are developed, making it hard for an administrator to maintain a complete and up-to-date list of harmful apps. And, given that 30 percent of malware targets zero-day vulnerabilities, a security breach could occur before the vulnerable programs are added to the blocklist.

Unfortunately, in the event of a zero-day attack, organizations will be left susceptible, regardless of their security strategy. The increasing increase in targeted attacks aimed at obtaining confidential data from organizations should likewise concern administrators. Predicting and stopping these types of assaults by blocklisting would be useless.

Application Allowlisting or Blocklisting

Application Allowlisting or Blocklisting is sometimes mistaken with Allowlisting and Blocklisting. Although application allowlisting and blocklisting are components of allowlisting and blocking, they function under more flexible rules.

Application Allowlisting

Application allowlisting is similar to an elite club membership, guaranteeing that only the most trustworthy IP addresses, domains, and apps are given the red-carpet treatment. It is the process of compiling a list of approved entities, such as domains and applications, that are permitted to access a specific resource or take a specific activity.

The United States National Institute of Standards and Technology (NIST) has released a Guide to Application Whitelisting, which proposes utilizing two of the following attributes together to define an application for whitelisting.

  • File Path permits all apps to execute within a given file path or directory, however it is a broad property that cannot prevent malicious software from operating in the correct location.

  • File Name permits a certain naming convention to be used but does not check for renamed dangerous files or malware-infected files.

  • File Size merely checks the file size and can easily allow malware with the right file size to execute.

  • A digital signature can provide a unique value to an application, but it may become obsolete when fixes and upgrades are performed.

  • Cryptographic Hash provides the most unique and least spoofable value for whitelisting, but it will be invalidated if the software is patched or updated.

Application Blocklisting

Application blocklisting: the ultimate antivirus or firewall. It's like having your squad of security guards, ready to face known aggressors. Consider a list of malicious IP addresses that are blocked from your network, guaranteeing that they never gain access. What about those spam email addresses? Blocklisting also helps to keep your inbox clean. 

Alternative Names

Allowlisting and Blacklisting as stated earlier can also be called Whitelisting and Blacklisting, While these are common terms, there's a growing movement to use more neutral alternatives. This shift reflects concerns that the color-based terms can be insensitive and perpetuate harmful associations.

Several platforms have already adopted new terminology. To ensure you understand the latest options within your security tools, here are some updated terms:


  • Whitelisting(Superseded)

  • Allow-listing

  • Permitted listing

  • Approved listing


  • Blacklisting(Superseded)

  • Denylist

  • Deny-list

  • Blocked list

  • Disapproved list


Both allowlisting and blocklisting offer valuable tools for managing access and security, each with distinct benefits and challenges.

Choosing the right approach depends on your specific needs and priorities. For maximum protection, consider a hybrid strategy that combines the strengths of both. Allowlisting provides a foundation of trust, while blocklisting offers a safety net against unforeseen threats.

Remember, security is an ongoing process, and regularly updating and adapting your approach is crucial to navigating the ever-evolving digital landscape. By understanding the advantages and limitations of each method, you can craft a defense that keeps your system secure, productive, and compliant.


The leader in client-side Web security. With Jscrambler, JavaScript applications become self-defensive and capable of detecting and blocking client-side attacks like Magecart.

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