New Rowhammer technique – Security Boulevard

Rowhammer is an attack technique involving accessing – i.e. “hammering” – rows of bits in memory, millions of times per second, in order to toggle bits in neighboring rows. . This is a side channel attack, and the result can be all kinds of chaos.

Well, there is a new improvement:

All previous Rowhammer attacks have hammered rows with uniform patterns, such as single-sided, double-sided, or n-sided. In all three cases, these “attacker” lines – that is, those that cause bit hopping in nearby “victim” lines – are consulted the same number of times.

Research published Monday presented a new technique from Rowhammer. It uses non-uniform patterns that access two or more rows of attackers with different frequencies. The result: All 40 randomly selected DIMMs from a test pool underwent bitflips, compared to 13 of 42 chips tested in previous work by the same researchers.


Non-uniform patterns work against refreshing the target row. Short for TRR, mitigation works differently from provider to provider, but typically tracks the number of times a line is accessed and reloads neighboring victim lines when there are signs of abuse. Overriding this defense puts additional pressure on chipmakers to mitigate a class of attacks that many people believed the newer types of memory chips to be resistant to.

*** This is a syndicated Schneier Security Bloggers Network security blog written by Bruce Schneier. Read the original post at:

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