Microsoft Vulnerable Driver Blocklist: Complete Guide

In the world of ciberseguridad, protect the operating system kernel Windows It is one of the most important priorities for both home users and businesses. Over the years, Microsoft has implemented increasingly sophisticated mechanisms to protect the kernel from threats, but attackers continue to seek entry points to execute privileged code. One of the most dangerous—and increasingly common—methods is to exploit vulnerabilities in the drivers loaded on the system, many of which are legitimate and digitally signed but contain security flaws that can be exploited.

To address this reality, Microsoft has developed the so-called Microsoft Vulnerable Driver Blocklist, which is intended to prevent the execution of dangerous drivers in the Windows kernel. This feature, increasingly present and enabled by default in the latest versions of the operating system, is a key part of the protection ecosystem comprised of both Windows Defender and other advanced security policies.

What is the Microsoft Vulnerable Driver Blocklist?

La Microsoft Block List of Vulnerable Drivers It is a defense mechanism that seeks to prevent certain drivers, identified as potentially unsafe or directly dangerous to the integrity of the system, from running in the Windows kernel. These drivers, although usually properly signed and distributed by legitimate manufacturers, have occasionally presented vulnerabilities that can be exploited by malicious software to gain elevated privileges, evade protection systems, or compromise the normal operation of the machine.

Microsoft maintains and updates this list in collaboration with manufacturers of hardware (IHV and OEM) and with the security community, so that it always includes drivers whose exploitation represents a real threat. Its main function is to automatically block the execution of these drivers to prevent privilege escalation, the introduction of rootkits or the manipulation of antimalware tools..

Why is a driver blocklist necessary?

Attackers have long since discovered that it is not always necessary to develop malware from scratch to gain low-level system control. The technique known as Bring Your Own Vulnerable Driver (BYOVD) exploits the existence of legitimate drivers with security flaws to deploy advanced threats.. This allows cybercriminals to install and load a vulnerable driver (often old but still signed) and then exploit it to gain access to internal operating system resources, disable antivirus software, extract credentials, or install rootkits.

These maneuvers have even been seen in ransomware operations and targeted attacks against large corporations. Microsoft has detected the systematic use of this technique by both advanced threat actors and basic malware developers., which highlights the need for a mechanism that controls and limits which drivers can run in the most critical environment of the system.

Collaboration between Microsoft and manufacturers to identify dangerous drivers

One of the strongest points of Microsoft's defense lies in its direct collaboration with major hardware manufacturers and independent software vendors. Whenever a vulnerability is discovered in a driver, Microsoft works with the manufacturer to inform them as soon as possible, include the driver in the block list if appropriate, and coordinate the release of an update or patch that resolves the issue.This allows, on the one hand, to protect users from running the vulnerable driver, and on the other hand, to ensure that new, fixed versions are distributed safely throughout the Windows ecosystem.

Developers and manufacturers can submit suspicious drivers directly to Microsoft for security analysis, or request patches and changes if a driver has been fixed after an update. The company offers specific resources and channels for submitting incidents, which speeds up the detection and rapid incorporation of new drivers to the list..

What types of drivers crash?

Microsoft's policy for defining which drivers should be included in this list is based on detecting those that meet at least one of the following criteria:

• They present known security vulnerabilities which can be exploited to elevate privileges or compromise the integrity of the Windows kernel.
• They exhibit malicious behavior, such as having been used to distribute malware, rootkits or harmful software.
• They include digital signature certificates used to sign malware or tools of hacking.
• They have practices that evade the Windows security model, although not strictly malicious, can be exploited by attackers to gain excessive control over the system.

Thanks to this approach, the list not only protects against active vulnerabilities, but also against the entire attack chain based on outdated or inadequately protected drivers.The presence of a driver in the list means that the operating system will block its loading and execution, thus preventing malware from exploiting it.

Blocklist Evolution: Integration and Updates

La Microsoft's block list of vulnerable drivers It has been progressively integrated into all modern versions of Windows. Since Windows 1809 version 10, it began as an optional feature for those users and environments that enabled advanced technologies such as Hypervisor-Protected Code Integrity (HVCI) or the so-called S mode. However, with the arrival of Windows 11 and especially with the 22H2 update, it has been enabled by default on all supported devices.

This means that All Windows 11 22H2 (and higher) users have blocklist protection automatically, without any additional configuration.. For older versions or on Windows 10, the activation of the list depends on the corresponding security feature, such as Smart App Control, S mode or HVCI, being enabled, although it can also be added manually through optional updates. Windows Update.

How often is the blocklist updated and how are new features distributed?

Microsoft updates the driver block list with each new major version of Windows., typically once or twice a year, but may also deploy additional updates through standard operating system maintenance. The latest versions of the blocklist are distributed simultaneously as optional Windows Update updates for users of Windows 10 (starting with version 20H2) and Windows 11 (21H2 and later).

However, if an administrator wants to always make sure that he is protected with the most recent version of the blocklist, he has tools such as App Control for Business, which allows you to apply the updated list of blocked drivers even before it arrives via standard update. Microsoft also publishes downloads updated file manuals, along with detailed instructions for its implementation.

How user protection works: Integration with Windows Defender and App Control

La blocklist It integrates its operation with other Windows defense measures, particularly Windows Defender and App Control. In the case of Defender, the system performs a thorough check on drivers that attempt to be installed, assesses their presence on the blacklist, and, if appropriate, blocks their execution and displays alerts in the Windows Security Center.

App Control for Business allows administrators to enforce the Microsoft block list using security policy policies.. While this is an advanced option geared toward businesses and professional environments, it's very useful for maintaining a consistent defense across your entire IT infrastructure. In fact, if it's not possible to enable certain features like S mode or HVCI, Microsoft specifically recommends blocking the list of dangerous drivers by using app control, although it is advisable to first test the policy in audit mode to avoid incompatibilities or accidental blocking of critical devices.

Step by step: How to manually download and apply the block list

For users or administrators who want to ensure they have the most current version of the lock file, Microsoft offers a manual procedure. The process typically involves downloading the App Control Policy Update Tool, obtaining the blocklist binaries, renaming the policy file to SiPolicy.p7b, copy it to the directory %windir%\system32\CodeIntegrity and run the update to activate the new policy. This way, any attempt to load a driver listed as vulnerable will be automatically stopped by the system.

To verify that the policy is operational, simply open the Event Viewer, go to the event log, and Microsoft – Windows – CodeIntegrity – Operational and filter by event ID 3099. There you can check the details of the applied policy and confirm that it corresponds to the most recent version.

Can blocking drivers cause compatibility issues?

One of the most frequently asked questions about this security feature is whether it could block necessary drivers and cause system failures. The answer is that, although the list has been carefully compiled to minimize conflicts, there is a possibility that, in very specific cases, blocking a driver could cause certain hardware or software to not work correctly., or even cause a blue screen (BSOD).

Therefore, Microsoft recommends that system administrators apply and test the policy, especially in audit mode, before fully enabling it, reviewing blocking events to rule out interference with essential work components.

How to enable or disable the block list from Windows Security

In newer versions of the operating system, managing the feature is easier than ever. Simply open the Windows Security app, navigate to "Device Security" and access the "Kernel Isolation" section..

There, the user will see the option to activate or deactivate the Microsoft's block list of vulnerable driversSimply change the status as desired and restart the device for the changes to take effect. This process is identical in Windows 11 22H2 and higher; in earlier versions, you may need to additionally enable the Memory Integrity or HVCI feature to enable protection.

Link to Attack Surface Reduction (ASR)

Kernel defense is not only based on the driver blocklist, but is part of a broader framework called Attack Surface Reduction (ASR), which encompasses a set of rules designed to minimize opportunities for exploitation by malware and hackers. One of the most recommended ASR rules, enabled by default in many environments, is precisely the one that blocks the abuse of vulnerable signed drivers.

The ASR rules system is integrated into Microsoft Defender for Endpoint and allows you to set policies to block, audit, or warn the end user. Each rule has its own unique GUID and can be configured individually from the Admin Center or using tools such as PowerShell.

List of ASR rules related to drivers and other common risks

In addition to the rule blocking vulnerable drivers, the ASR rule package includes many other measures relevant to corporate and personal security:

• Prevent Adobe Reader from creating child processes.
• Prevent Office applications from creating child processes or injecting code into other processes.
• Block the execution of potentially obfuscated scripts.
• Prevent JavaScript or VBScript from launching downloaded executable content.
• Block unsigned processes from units USB or copied/impersonated system tools.
• Block the creation of dangerous WebShells or API calls from Office macros.
• Using advanced protections against ransomware and other sophisticated attacks.

For each rule, you can set whether it should be in blocking, auditing, or warning mode, thus allowing it to be adapted to the needs of each organization.This flexibility is key to maintaining security without sacrificing compatibility or daily workflow.

How are ASR rules applied and managed?

ASR rules can be applied through different mechanisms:

• From the console Microsoft Defender for Endpoints, setting policies at the company, group, or device level.
• Using Microsoft Intune, which allows centralized management of all rules and their distribution by profiles.
• Locally, using PowerShell to activate or audit a specific rule on a computer.

Each rule is identified by a unique GUID, and state combinations can be set:
unconfigured, blocked, audit or warning. Warning mode is especially useful in environments where you want to inform the user of the risk without automatically blocking the action, allowing them to make a decision under warning.