Recent advancements in cyber-attack methodologies have seen the emergence of a novel network-based variant of the notorious Rowhammer attack, referred to as “Nethammer.” This approach exploits vulnerabilities in dynamic random access memory (DRAM) through network cards, and it capitalizes on remote direct memory access (RDMA) channels to manipulate memory states without needing direct access to the target machine. It represents a significant evolution following the initial network-based Rowhammer attack known as “Throwhammer,” reported the previous week.
The Nethammer attack introduces a second technique that enables security researchers to target systems that utilize uncached memory while processing network requests. This new method diverges from the insights garnered by a separate group of researchers who previously unveiled the Meltdown and Spectre CPU vulnerabilities. While both research teams contribute to understanding vulnerabilities in memory architecture, they operate independently in their discoveries.
A critical understanding of the Rowhammer vulnerability involves its impact on contemporary DRAM chips, which are susceptible to “bit flipping.” By continuously accessing specific memory rows, an attacker can inadvertently affect adjacent rows. Previous exploits of the Rowhammer vulnerability necessitated physical access to a machine to escalate privileges to kernel-level or achieve remote code execution. In contrast, Nethammer allows for arbitrary code execution remotely, provided there is a sufficient network connection between the attacker and the victim’s system.
This technique functions by overloading memory locations used during packet processing, causing a significant number of accesses that lead to disturbance errors in DRAM. Ultimately, this uncontrolled flipping of memory bits permits attackers to orchestrate data manipulation, granting undue control over the compromised system.
To successfully carry out a Rowhammer attack, it is essential that memory accesses are executed via the main memory and bypass the cache. The research paper elaborating on this technique indicates that the cache can inhibit the efficacy of such an attack, leading researchers to develop methods that facilitate direct interaction with DRAM, thus enabling the row conflicts necessary for exploitation.
Various cache-bypass techniques have been assessed in the context of the Nethammer attack. Researchers tested scenarios involving a kernel driver programmed to flush and reload addresses upon receiving packets, Intel Xeon CPUs employing Intel Cache Allocation Technology (CAT) for rapid cache eviction, and the use of uncached memory on ARM-based devices. The researchers successfully demonstrated the effectiveness of these approaches, achieving a bit flip within approximately 350 milliseconds by transmitting UDP packet streams at rates approaching 500 Mbit/s.
Notably, the Nethammer technique’s unique design, which does not rely on any form of attack code on the victim’s system, poses challenges for traditional countermeasures designed to mitigate such threats. As this method leverages inherent hardware vulnerabilities, software patches alone will not address the core issue.
As cyber threats continue to evolve, the Rowhammer vulnerability remains a pertinent concern. Researchers assert that the potential for substantial damage stemming from these exploits is real and imminent. For a thorough examination of this groundbreaking attack vector, readers can consult the published paper titled “Nethammer: Inducing Rowhammer Faults through Network Requests,” which offers an in-depth analysis of the methodology.
Given the potential impact on a wide array of systems, business owners and cybersecurity professionals are advised to remain vigilant and informed about such vulnerabilities. As outlined in the MITRE ATT&CK framework, techniques including initial access, privilege escalation, and possibly even lateral movement can be associated with the Nethammer attack, emphasizing the need for comprehensive security measures to mitigate these evolving threats.
As cyber threats continue to escalate, understanding the implications of vulnerabilities like Rowhammer is crucial in fostering a robust cybersecurity posture. For ongoing updates and insights into the realm of data breaches and cyber risks, following platforms such as Google News and social media channels dedicated to cybersecurity could greatly aid organizations in maintaining awareness of the landscape.
