A new technique for hacking DRAM could expose DDR4 RAM to attacks and system hijacking. Thankfully, Google is hoping that publicizing this discovery will speed up the fix.

This software is a new variant of a known vulnerability called Rowhammer. A vanilla version of this software compromises data scattered across RAM memory cells by giving hackers the ability to access one adjacent row and modify the contents of other memory addresses by sending multiple access requests.

This has existed for some time and, according to Neowin, was made possible thanks to "an electrical coupling phenomenon in silicon chips that bypasses software and hardware-based protections."

Previously, DDR3 chips allowed DRAM manufacturers to protect against Rowhammer hacking by implementing logic to detect and block cheating. However, with the advent of DDR3 chips, DRAM manufacturers were able to protect against Rowhammer hacking. Now, however, with the advent of DDR4, it is clear that the Rowhammer threat still operates through TRRespass and other methods.

According to Google's harbingers, there is now a new "half-double" Rowhammer technique that is even more dangerous and has been shown to outperform its predecessor by at least one more row, although it is not as effective at accessing cache depths. Still, it may be able to access deeper rows, exposing more data. [Unlike TRRespass, which exploits blind spots in manufacturer-dependent defenses, Half-Double is a property inherent in the underlying silicon substrate. This likely indicates that the electrical coupling responsible for Rowhammer is a property of distance, effectively getting stronger and longer-range as the cell geometry gets smaller."

"More than two distances are possible.

All of this is out in the open to encourage collaboration to plug compromises as quickly as possible. Google is also working with industry partners like semiconductor standards body JEDEC to get the ball rolling. You can see the results so far here and here.