Bring Your Own Vulnerable Driver (BYOVD) Attacks: A Comprehensive Analysis and Mitigation Strategies

Abstract

The cybersecurity landscape has witnessed a significant evolution in attack methodologies, with adversaries increasingly targeting kernel-level vulnerabilities to bypass traditional security defenses. One such sophisticated technique is the Bring Your Own Vulnerable Driver (BYOVD) attack, where malicious actors exploit legitimate, signed drivers to gain deep kernel-level access, thereby circumventing security mechanisms like Microsoft Defender. This research report delves into the technical specifics of BYOVD attacks, examining the types of vulnerable drivers exploited, mechanisms of privilege escalation, advanced detection techniques, and comprehensive mitigation strategies to prevent such kernel-level circumvention of defenses.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

1. Introduction

In recent years, cyber adversaries have demonstrated a marked shift towards exploiting kernel-level vulnerabilities to undermine system security. The BYOVD attack vector exemplifies this trend, leveraging trusted components within the operating system to achieve malicious objectives. This report aims to provide an in-depth analysis of BYOVD attacks, offering insights into their operational mechanics and proposing effective countermeasures.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

2. Background and Evolution of BYOVD Attacks

2.1. Definition and Mechanism

A BYOVD attack involves the deployment of a legitimate, signed driver that contains known vulnerabilities. Once loaded into the system, this driver operates with high-level privileges, allowing attackers to execute arbitrary code in kernel mode. This access facilitates the disabling of security features, such as antivirus and endpoint detection and response (EDR) systems, thereby enabling further malicious activities without detection.

2.2. Historical Context

The concept of exploiting signed drivers is not novel. Early instances date back to at least 2012, with malware like “Slingshot” employing BYOVD techniques. Over the years, various advanced persistent threat (APT) groups and ransomware operators have adopted this strategy, underscoring its effectiveness in evading detection mechanisms. (arstechnica.com)

Many thanks to our sponsor Esdebe who helped us prepare this research report.

3. Technical Analysis of BYOVD Attacks

3.1. Exploited Vulnerable Drivers

Adversaries often target drivers associated with legitimate software that have known vulnerabilities. Examples include:

• ThrottleStop Driver (rwdrv.sys): A legitimate driver used for CPU performance tuning, which has been exploited to gain kernel-level access. (csoonline.com)

• MSI Afterburner Driver (RTCore32.sys and RTCore64.sys): Drivers for a graphics card utility, exploited to bypass security solutions. (esecurityplanet.com)

• Genshin Impact Anti-Cheat Driver (mhyprot2.sys): A deprecated anti-cheat driver used to gain further access within Windows systems. (arstechnica.com)

3.2. Privilege Escalation Mechanisms

The exploitation process typically involves:

1. Driver Installation: The attacker installs the vulnerable driver, often using administrative privileges.

2. Privilege Escalation: Once loaded, the driver allows the execution of arbitrary code in kernel mode, facilitating the disabling of security features.

3. Malware Deployment: With defenses disabled, the attacker deploys malware, such as ransomware, to achieve their objectives. (itinnovationstation.com)

3.3. Evasion of Detection Mechanisms

BYOVD attacks are particularly effective against traditional security measures due to:

• Use of Signed Drivers: Exploiting drivers that are digitally signed by trusted entities allows the malicious driver to bypass signature-based detection mechanisms.

• Kernel-Level Access: Operating at the kernel level enables the attacker to disable or bypass security processes, rendering endpoint security solutions ineffective. (crowdstrike.com)

Many thanks to our sponsor Esdebe who helped us prepare this research report.

4. Advanced Detection Techniques

4.1. Memory Integrity Checks

Implementing memory integrity checks can help detect unauthorized code running in kernel mode. This involves:

• Monitoring Kernel Memory: Regularly scanning kernel memory for anomalies or unauthorized code injections.

• Integrity Verification: Using cryptographic hashes to verify the integrity of kernel-mode code and drivers. (crowdstrike.com)

4.2. Driver Integrity Monitoring

Monitoring driver installations and loads can aid in early detection:

• Auditing Driver Loads: Keeping a log of all driver load events to identify unauthorized or unexpected drivers.

• Blocklisting Vulnerable Drivers: Maintaining and enforcing blocklists of known vulnerable drivers to prevent their loading. (itinnovationstation.com)

Many thanks to our sponsor Esdebe who helped us prepare this research report.

5. Mitigation Strategies

5.1. Regular Driver Audits and Updates

Organizations should:

• Conduct Regular Audits: Periodically review and update drivers to ensure they are free from known vulnerabilities.

• Apply Vendor Patches: Promptly apply patches and updates provided by hardware and software vendors. (base4sec.com)

5.2. Strengthening Administrative Privileges

Implementing strict access controls can prevent unauthorized driver installations:

• Least Privilege Principle: Ensure that users have the minimum necessary privileges to perform their tasks.

• Access Control Policies: Enforce policies that restrict the installation and loading of unauthorized drivers. (base4sec.com)

5.3. Kernel Protection Mechanisms

Activating built-in security features can enhance system defenses:

• Memory Integrity: Enable features like Hypervisor-Protected Code Integrity (HVCI) to protect against unauthorized code execution in kernel mode. (crowdstrike.com)

• Driver Signature Enforcement: Ensure that only signed drivers are loaded into the system. (bleepingcomputer.com)

5.4. Endpoint Detection and Response (EDR)

Deploying EDR solutions can aid in detecting and responding to suspicious activities:

• Behavioral Monitoring: Monitor for unusual driver load events or attempts to disable security processes.

• Process Termination Alerts: Set up alerts for the termination of critical security processes. (itinnovationstation.com)

Many thanks to our sponsor Esdebe who helped us prepare this research report.

6. Conclusion

BYOVD attacks represent a sophisticated and evolving threat in the cybersecurity domain. By exploiting legitimate, signed drivers, adversaries can gain deep kernel-level access, effectively disabling security defenses and facilitating further malicious activities. A multi-layered defense strategy, encompassing regular driver audits, strict access controls, kernel protection mechanisms, and advanced detection techniques, is essential to mitigate the risks associated with BYOVD attacks. Continuous vigilance and adaptation to emerging threats are imperative to maintain robust system security.

Many thanks to our sponsor Esdebe who helped us prepare this research report.

References

• (csoonline.com) GuidePoint reports on Akira ransomware exploiting legitimate Windows drivers.

• (base4sec.com) Base4 Security discusses the dangers of signed drivers in BYOVD attacks.

• (bleepingcomputer.com) BleepingComputer reports on Microsoft-signed malicious Windows drivers used in ransomware attacks.

• (crowdstrike.com) CrowdStrike Falcon prevents multiple vulnerable driver attacks in real-world intrusion.

• (arstechnica.com) Ars Technica discusses how a Microsoft blunder opened millions of PCs to potent malware attacks.

• (esecurityplanet.com) eSecurity Planet reports on ransomware group using vulnerability to bypass EDR products.

• (itinnovationstation.com) ITInnovationStation discusses AuKill and the BYOVD tactic: a tale of attack and defense.

• (cybersecuritynews.com) CybersecurityNews reports on Akira ransomware using Windows drivers to bypass AV/EDR in SonicWall attacks.

• (sangfor.com) Sangfor discusses BYOVD attacks in 2023.

• (packetlabs.net) Packetlabs explains what BYOVD attacks are.

• (electronicsandict.com) Electronics and ICT explains what BYOVD attacks are.

• (cymulate.com) Cymulate discusses defending against BYOVD attacks.