BYOVD Attacks Explained

BYOVD, (short for Bring Your Own Vulnerable Driver) is a strategy where attackers use legitimately signed but exploitable drivers to gain privileged access to systems. In this comprehensive guide, BYOVD is explained in detail highlighting why signed drivers, once trusted, have become a weapon for cybercriminals.

BYOVD Explained: Understanding BYOVD

What Does BYOVD Stand For?

BYOVD stands for Bring Your Own Vulnerable Driver. It refers to a technique where attackers loads a driver one that is digitally signed but has known security flaws to gain kernel-level access to a Windows system. Unlike malware that sneaks in through fake software or phishing links, BYOVD abuses the trust system of the operating system itself. A byovd attack is a sophisticated threat technique used by advanced cyber threat groups to gain kernel-level access by exploiting vulnerable, yet legitimately signed, drivers.

The Origin and Evolution of BYOVD Attacks

This technique has been around for years but remained under the radar. Initially seen in penetration testing circles and proof-of-concept research, it has evolved into a mainstream threat leveraged by advanced persistent threats (APTs) and ransomware gangs alike. Various threat groups and ransomware gangs have adopted BYOVD attacks as part of their arsenal, using them in targeted cyber espionage and cyberattack campaigns.

Why Hackers Love Signed Drivers

Because Windows allows drivers with valid signatures to run in kernel mode, attackers exploit signed-but-vulnerable drivers to gain privileged access. These drivers create a legitimate pathway from user mode into the kernel, enabling privilege escalation and manipulation of system protections. Their valid signatures also reduce suspicion, making it easier for malicious drivers to load and operate without immediately triggering UAC, Secure Boot, or antivirus defenses.

In technical terms
Windows trusts digitally signed drivers and lets them load into kernel space. Attackers abuse signed but vulnerable drivers as a trusted interface: from user mode they call the driver’s IOCTLs to read/write kernel memory, execute code at Ring 0, or disable security hooks and protections. While the signature helps the driver load and evade some heuristics, the primary advantage is that the driver bridges user-mode and kernel-mode, giving attackers direct access to the highest privilege level, allowing them to stop processes or execute code in memory.

How BYOVD Attacks Work

Driver Signing Basics

To load into Windows, kernel-mode drivers must be digitally signed by a trusted Certificate Authority (CA). Drivers must also be properly installed for the operating system to recognize and use them, and managing installed drivers is crucial for security. Windows drivers are a common target for these attacks due to their high level of system access.

Exploiting Legitimate Signatures

Attackers take advantage of the fact that many old drivers were signed but later found to contain serious vulnerabilities. If a CA hasn’t revoked the certificate, Windows still accepts the driver, opening the door for compromise. Kernel drivers with vulnerabilities are often targeted in own vulnerable driver attacks, allowing attackers to achieve kernel level privilege escalation.

How Attackers Load Malicious Drivers

1. Attackers implant a vulnerable driver onto the targeted system.
2. Load the driver to access kernel-mode (this required admin privileges).
3. Disable security controls, install rootkits, or tamper with system files.

Attackers often use specialised tools to load malicious drivers and bypass security controls. Attackers may use their own malicious driver or exploit drivers installed on the system to run malware and perform privilege escalation.

The Power of Kernel-Level Access

What is Kernel-Mode Privilege? – Kernel mode is the highest level of access on a system. Unlike user-mode apps, kernel-mode components can read/write to any memory address, terminate processes, or even completely disable antivirus. With kernel-level access, attackers can perform malicious actions such as tampering with kernel memory and accessing sensitive data.

How Drivers Bypass OS-Level Protections – Signed drivers are given high trust. This allows them to turn off Windows Defender, bypass virtualization-based security (VBS), or manipulate process privileges, all without triggering alarms. These attacks are often analyzed in depth by security researchers to understand the full scope of malicious activity enabled by kernel-level exploits.

Real-World Exploits Using BYOVD – APT groups like Lazarus, APT41, and ransomware gangs such as BlackByte and LockBit have all used BYOVD in their operations. Commonly exploited drivers include those from GIGABYTE, MSI, and even Intel.

Why Signed Drivers Are Dangerous

Trust Models in OS Security – Operating systems rely on a chain of trust. If a driver is signed, it’s assumed to be safe. This blind trust is what BYOVD exploits so effectively. However, legitimate drivers, while trusted, can contain driver vulnerabilities that are exploited in BYOVD attacks.

Digital Signatures: Not Foolproof – Many attackers use drivers that were signed years ago and still carry valid certificates. Revoking these is a slow and bureaucratic process, allowing the threat to persist. Vulnerable driver BYOVD techniques specifically target these legitimate drivers with known flaws.

The Problem with Legacy Certificates– Many legacy drivers from discontinued products still work on modern systems. Their certificates were never revoked, creating a massive loophole.

Recent Cases of BYOVD Attacks

APTs Using BYOVD (APT41, Lazarus Group) – APT41 famously used a vulnerable driver from a gaming software vendor to disable security tools during espionage campaigns. Various threat actors, including top tier APT groups such as Turla and the Equation Group, have also been observed using BYOVD techniques.

Ransomware Campaigns Involving BYOVD – BlackByte 2.0 was observed using a vulnerable MSI Afterburner driver to bypass endpoint detection tools before deploying ransomware. Ransomware groups and other threat actors are increasingly leveraging BYOVD attacks in their campaigns.

Nation-State Threat Actors – Reports from Mandiant and CrowdStrike indicate nation-states are heavily investing in BYOVD toolkits to silently infiltrate critical infrastructure.

BYOVD vs. Other Attack Vectors

BYOVD vs. DLL Injection

Unlike DLL injection (which is mostly user-mode), BYOVD operates at the kernel level, making it more powerful and harder to detect. BYOVD techniques are more difficult to detect due to their operation at the kernel level, as attackers exploit vulnerable driver attacks using the BYOVD technique to bypass traditional security measures.

BYOVD vs. Exploiting Zero-Day Vulnerabilities

BYOVD doesn’t require zero-days. It uses publicly known vulnerable drivers, making it cheaper and easier for attackers to deploy. Although when new vulnerable drivers are found they could be considered a zero-day and could be exploited whilst they are running on people devices.

BYOVD vs. Fileless Malware

While fileless malware evades disk-based detection, BYOVD avoids behavior-based and signature-based detection by using trusted files.

How to Detect BYOVD Attacks

Behavior-Based Detection – Look for unusual behaviors like unexpected driver loads, especially from non-standard paths or legacy drivers. Collecting and analyzing data from system logs and telemetry is essential for detecting BYOVD attacks, as data-driven insights help identify anomalies related to vulnerable drivers or malicious activity.

Leveraging EDR and XDR – Advanced tools like SentinelOne, CrowdStrike, and Microsoft Defender XDR can spot anomalies in driver behavior and block suspicious loading attempts. Endpoint security products and other security products play a crucial role in identifying and blocking malicious driver activity.

Memory and Driver Integrity Monitoring – Kernel-level monitoring tools that use memory forensics and integrity checks can flag unauthorized driver installations. Advanced security software can help monitor for unauthorized driver installations and suspicious behavior.

Mitigating BYOVD Risks

• Blocking Known Bad Drivers – Use Microsoft’s blocklist of known vulnerable drivers, and ensure it’s enabled via HVCI (Hypervisor-Enforced Code Integrity). This blocklist is a critical security feature provided by Microsoft’s to help prevent BYOVD attacks by blocking the execution of vulnerable drivers.
• Using Microsoft’s HVCI & SI – Enable HVCI and Secure Isolation features in Windows to prevent unauthorized driver loading and enforce code integrity. Enabling these features significantly strengthens the overall security posture of the organization.
• Implementing Secure Boot and Driver Policies – Secure Boot ensures only signed code runs at boot. Combine it with Group Policy restrictions to block unsigned or outdated drivers.

BYOVD in the Supply Chain

• Driver Supply Chain Vulnerabilities – Vendors may unknowingly ship drivers with flaws. Attackers can intercept the development pipeline or exploit third-party vendors. Device drivers act as connectors between the operating system and the physical parts of a computer, such as keyboards and video cards, making their security critical.
• Impact on OEMs and Third-Party Vendors – Driver signing responsibilities now fall heavily on hardware vendors, many of whom lack mature security practices, making them soft targets. Vulnerabilities in device drivers can be exploited to compromise the physical parts of targeted systems.

Tools and Techniques Hackers Use

Malicious actors and threat actors develop and use specialized tools to exploit driver vulnerabilities, enabling them to bypass security controls and escalate privileges.

Common Exploited Drivers

• GIGABYTE gdrv.sys
• MSI Afterburner
• ASUS GPU Tweak
• Intel PMx Driver

Tools Like KDMapper and Ghosting Techniques

Hackers use KDMapper to load drivers into memory without signing. Ghosting allows deleting files post-execution, evading analysis. Some advanced attacks by threat actors may also involve malicious firmware, which helps them persist on a system and evade detection.

Reverse Engineering for Exploits

Many attackers reverse engineer drivers to find exploitable I/O control codes (IOCTLs) they can abuse with user-mode payloads.

BYOVD in Malware-as-a-Service

• How Malware Kits Integrate BYOVD – Malware-as-a-Service (MaaS) offerings now include driver loader modules, making BYOVD accessible even to low-skilled hackers.
• Dark Web Markets for Signed Drivers – Signed drivers are sold on forums and marketplaces, often bundled with exploit code and obfuscation techniques.

Challenges for Blue Teams

• Forensics Complexity – Kernel-level attacks leave fewer artifacts, making incident response and root cause analysis extremely difficult.
• Limited Visibility at Kernel Level – Even EDR solutions struggle to provide visibility at kernel depth without performance trade-offs.
• Alert Fatigue and False Positives -Security teams face alert overload, making it easy for BYOVD incidents to slip through the cracks.

BYOVD in Endpoint Security

• Endpoint Protection Limitations – Traditional antivirus tools rely on signature detection, which fails against signed drivers with valid certs.
• Role of Next-Gen Antivirus – NGAVs that leverage behavioral AI and cloud-based analysis are better equipped to handle BYOVD threats.
• Hardware-Based Security Measures – Trusted Platform Modules (TPM) and modern CPUs with hardware-backed security can prevent unauthorized code execution at boot level.

The Future of Driver-Based Attacks

• Increasing Sophistication of BYOVD – Expect polymorphic drivers, signed driver obfuscation, and even fileless driver injections to become more common.
• AI-Powered Evasion – Malware authors are now using AI to bypass driver detection tools by mimicking legitimate software behavior.
• How OS Vendors Are Responding – Microsoft and Linux vendors are pushing updates, auto-blocklists, and mandatory signing changes to curb BYOVD risks.

FAQs on BYOVD Explained

• What is BYOVD and how does it work?
  BYOVD stands for Bring Your Own Vulnerable Driver, where attackers use signed but flawed drivers to gain privileged access to systems.
• Why are signed drivers dangerous in cybersecurity?
  Signed drivers are trusted by the OS. If vulnerable, they can be misused to bypass security protections undetected.
• Can antivirus tools detect BYOVD attacks?
  Traditional antivirus struggles, but advanced EDR and XDR platforms can detect abnormal driver behavior.
• How do I protect my system from BYOVD?
  Enable HVCI, use driver blocklists, implement Secure Boot, and monitor for unusual kernel activity.
• Are BYOVD attacks common in 2025?
  Yes, BYOVD attacks have grown significantly, especially in ransomware and APT campaigns.
• Can BYOVD be prevented entirely?
  Not entirely, but risks can be greatly reduced with layered defenses, proper configuration, and monitoring.

Conclusion

BYOVD, once an obscure tactic, has now emerged as a primary attack vector in 2025. By exploiting the operating system’s trust in signed drivers, hackers can gain unparalleled access to systems and evade most defenses. Organizations must understand this threat, monitor their environments carefully, and implement proactive controls to mitigate it.