Updated ZenHammer would be the perfect name for a heavy metal band, but unfortunately it's an AMD-focused variant of the decade-old Rowhammer attack that compromises computers by flipping bits of memory.
ZENHAMMER attacks AMD Zen
Rowhammer was first proposed in a paper [PDF] published in June 2014 by researchers at Carnegie Mellon University and Intel. It's a technique for activating rows of DRAM cells—"hammering" them—in a way that destroys the contents of adjacent memory cells. These flaws then enable further exploitation, potentially allowing privilege escalation, access to kernel secrets, and breaking the boundary between virtual machines and hosts.
Until now, Rowhammer has mainly been a concern for those using processors from Intel, and to a lesser extent ARM hardware. Now it's AMD's turn, with ZenHammer, although limitations are in place, we learn.
Boffins from ETH Zurich – Patrick Jattke, Max Wipfli, Flavien Solt, Michele Marazzi, Matej Bölcskei and Kaveh Razavi – have devised a way to induce bit flips on AMD Zen 2 and Zen 3 systems with DDR4 memory despite the deployment of a defensive technique called Target Row Refresh.
