Rowhammer is an unintended side effect in dynamic random-access memory (DRAM) that causes memory cells to leak their charges and interact electrically between themselves, possibly leaking the contents of nearby memory rows that were not addressed in the original memory access. This circumvention of the isolation between DRAM memory cells results from the high cell density in modern DRAM, and can be triggered by specially crafted memory access patterns that rapidly activate the same memory rows numerous times.
The row hammer effect has been used in some privilege escalation computer security exploits, and network-based attacks are also theoretically possible in a fast network connection between the attacker and victim.
Academics Announce New Protections Against Spectre and Rowhammer Attacks
Academics from multiple universities have announced fixes for two severe security flaws known as Spectre and Rowhammer.
Both these fixes are at the software level, meaning they don’t require CPU or RAM vendors to alter products, and could, in theory, be applied as basic software patches.
Spectre v1 fix for Linux
The first of these new mitigation mechanisms was announces on Thursday, last week. A research team from Dartmouth College in New Hampshire says it created a fix for Spectre Variant 1 (CVE-2017-5753), a vulnerability discovered at the start of the year affecting modern CPUs.
Their fix uses ELFbac, an in-house-developed Linux kernel patch that brings access control policies to runtime virtual memory accesses of Linux processes, at the level of ELF binary executables.
In an email to Bleeping Computer, a Dartmouth College spokesperson said the team is currently working on a paper to describe the research in more depth, and a dedicated website that will feature more details will be completed over the next couple of days.
Rowhammer software-level fix
The second fix for a major flaw announced last week came on Saturday from the Systems and Network Security Group at VU Amsterdam.
Researchers announced a new technique called ZebRAM that they said is a comprehensive software protection against Rowhammer attacks. No details are currently available about this new technique outside the tweet below and the name of an upcoming research paper.
Rowhammer attacks have been a problem since 2014. Researchers have discovered a wide range of methods for launching Rowhammer attacks, and defenses put in place between 2014 and 2016 have been proven to be incomplete in October 2017.
Red Hat releases Spectre v1 scanning tool
The tool was developed by engineers from Red Hat, and hence, like the ELFBac tool, is only meant for Linux systems.
The tool currently only supports the x86_64 and AArch64 architectures, according to a Red Hat blog post that also includes a small tutorial on how software devs can use it to detect areas of their code that could be exploited via Spectre v1.
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