Security News > 2020 > March > TRRespass research reveals rowhammering is alive and well
TRR is short for Target Row Refresh, a high-level term used to describe a series of hardware protections that the makers of memory chips have been using in recent years to protect against rowhammering.
Incidentally, reading out a row essentially wipes its value by discharging it, so immediately after any read, the row is refreshed by saving the extracted data back into it, where it's ready to be accessed again.
In 64ms you can trigger an enormous number of memory reads along one memory row, and this may generate enough electromagnetic interference to flip some of the stored values in the rows on either side of it.
TRR is a simple idea: instead of ramping up the refresh rate of memory rows for the entire chip, the hardware tries to identify rows that are being accessed excessively, and quietly performs an early refresh on any nearby rows to reduce the chance of them suffering deliberately contrived bit-flips.
At least part of the issue is down to the race to squeeze more and more performance out of the hardware we've already got, because faster processors mean we can hammer memory rows more rapidly than ever, while higher-capacity RAM modules gives us more rows to hammer at any time.