A recently identified strain of ransomware is forcing a critical reevaluation of enterprise security postures by demonstrating a significant leap in attack efficiency. Dubbed “Reynolds” by security researchers, this new threat has pioneered an all-in-one attack methodology, bundling a vulnerable driver directly within its primary payload. This strategic consolidation of tools marks a concerning evolution of the “bring-your-own-vulnerable-driver” (BYOVD) technique, a method cybercriminals use to gain deep system access. By merging the tools needed to disable security with the malicious code that encrypts data, attackers can now execute their campaigns with unprecedented speed and stealth, presenting a formidable challenge to even the most sophisticated endpoint defense solutions and signaling a new phase in the ongoing cybersecurity arms race.
The Evolution of Evasion Tactics
The bring-your-own-vulnerable-driver technique has become a favored tool for sophisticated threat actors seeking to bypass modern security defenses. In a conventional BYOVD attack, an adversary first gains a foothold on a target system and then introduces a legitimate, digitally signed, but known-to-be-vulnerable third-party driver. Because these drivers operate at the kernel level—the core of the Windows operating system—they run with the highest possible privileges. This elevated access allows the attacker to execute specialized evasion tools, often called “EDR killers,” which are designed to systematically terminate the processes of Endpoint Detection and Response (EDR) platforms and other security software. By effectively disabling the digital alarm system before the main intrusion, attackers can proceed with their objectives unhindered, compelling organizations to adopt complex, layered security strategies in the hope that at least one defense mechanism remains unrecognized and active.
What sets the Reynolds ransomware apart is its radical departure from this established, multi-stage attack sequence. Traditionally, ransomware operators or their affiliates would first deploy a standalone EDR killer tool, such as the publicly available “AuKill,” to methodically neutralize a system’s defenses. Only after confirming that the security software had been successfully disabled would they proceed to deliver the separate ransomware payload to encrypt the victim’s files. The attack investigated by a joint threat hunter team, which was initially misattributed to the Black Basta group, revealed a far more streamlined process. The Reynolds payload had the vulnerable NsecSoft NSecKrnl driver embedded directly within it, a component tied to a vulnerability disclosed just a month prior. This bundling fuses the defense evasion and data encryption stages into a single, unified, and nearly instantaneous action, fundamentally altering the attack timeline.
A Dangerous New Advantage for Attackers
This integrated approach offers several distinct strategic benefits to threat actors, reflecting a calculated move to overcome improving defensive capabilities. The primary advantage is enhanced stealth. Deploying two separate files—the driver and the ransomware—creates two distinct opportunities for security systems to identify and flag suspicious activity on the network or endpoint. By contrast, dropping a single, combined file is a “quieter” operation that presents a much smaller surface for detection. Secondly, this method significantly increases the speed of the attack from initial compromise to final encryption. By eliminating the time gap between disabling the EDR and executing the ransomware, attackers effectively close the window of opportunity for security operations teams to intervene. In a conventional scenario, an alert about a suspicious driver might give defenders a chance to isolate the machine, but the bundled payload initiates encryption almost simultaneously with the disabling of defenses, making such manual or automated intervention profoundly more challenging.
The emergence of this technique aligns with a broader trend observed over the past two years: a marked increase in the use of “impairment techniques” by ransomware actors. This shift is a direct response to the improved capabilities of security vendors in detecting the precursor activities and reconnaissance patterns that typically precede a full-blown ransomware deployment. As EDR platforms have become more adept at identifying these initial signals, attackers have been forced to evolve their evasion tactics, with BYOVD emerging as a highly effective method. The innovation by the Reynolds group—bundling the driver into the payload—could make such attacks highly attractive to affiliates in the Ransomware-as-a-Service (RaaS) ecosystem. A self-contained package that requires fewer steps to deploy simplifies the entire process, lowering the technical barrier for less sophisticated cybercriminals and thereby increasing the overall efficiency and scalability of ransomware operations globally.
The Reality of an Imperfect Attack
Despite the sophistication of this new all-in-one technique, the specific attack analyzed by researchers was only partially successful, offering a glimmer of hope for defenders. According to intelligence analysts, the threat actors did manage to encrypt some files on the targeted system, causing a degree of damage. However, the primary goal of the embedded driver—to terminate the installed security product—appears to have failed, as the endpoint protection continued to function after the attack was initiated. This partial failure underscores the ongoing and dynamic cat-and-mouse game being played between attackers and defenders. It demonstrates that even novel and well-designed offensive techniques may not be universally effective against every security solution, and that robust, multi-layered defenses can still disrupt advanced attack chains, even when one component of the defense is directly targeted for neutralization.
This incident also casts a bright light on the persistent and difficult challenge of managing vulnerable drivers across the entire software ecosystem. The problem extends far beyond this single case. In a separate, recent event detailed by security firm Huntress, attackers were able to weaponize a driver for the EnCase digital forensics suite. Shockingly, threat actors successfully exploited this driver even though its security certificate had been revoked more than a decade earlier, pointing to exploitable gaps in Microsoft’s Driver Signature Enforcement feature. This illustrates a critical and systemic weakness: even when a driver is known to be vulnerable or its certificate is officially revoked, the mechanisms intended to prevent its execution are not foolproof. This reality leaves a lingering and dangerous attack surface that sophisticated adversaries are more than willing to exploit to achieve their objectives.
A Call for Systemic Change
The defensive measures currently in place, while valuable, have proven to be largely reactive in the face of these evolving threats. Major vendors have taken steps to mitigate the risk; for instance, Microsoft offers the Vulnerable Driver Blocklist, a security feature designed to prevent the loading of drivers that have been identified in past malicious campaigns. Security firms, in turn, configure their products to block all known vulnerable drivers as they are discovered. However, experts widely agree that such blocklists are an inherently reactive defense. They can only prevent attacks that use a previously identified and cataloged vulnerable driver. This approach offered no protection against zero-day exploits or, as seen in the Reynolds case, the initial weaponization of a newly discovered vulnerable driver before it has been added to any blocklist, leaving a critical gap in defenses.
Ultimately, the analysis of this incident led to a strong consensus among security experts: more proactive and systemic measures were needed from operating system vendors, particularly Microsoft, to address the root cause. It was argued that decisive action was required to address the widespread abuse of signed drivers, with one significant proposed step being the strict prevention of Windows from loading any driver with a revoked certificate. While this seemed like an obvious security improvement, researchers acknowledged the immense complexity of implementing such a change. A strict policy could have had unintended negative consequences, such as causing system instability or breaking legitimate legacy applications that relied on those older drivers. This tension between security and backward compatibility underscored the central challenge that had long defined the effort to mitigate the BYOVD threat.