From: Georgi Guninski <guninski@guninski.com>
   On Wed, Sep 16, 2015 at 11:46:26PM -0400, grarpamp wrote:
   >> Some paper has said systems using ECC RAM are resistant / immune
   >> to rowhammer.
   >> There is still a fair bump in cost for ECC system
   >> however once you've seen your first syslog entry
   >> you forget about the cost. Regardless of rowhammer.
   >ECC appears controversial:
     [1]http://blog.erratasec.com/2015/03/some-notes-on-dram-rowhammer.htm
   l
   >Update: This is really just meant as a primer, as background on the
   i>ssue, not really trying to derive any conclusions. I chatted a bit
   >Chris Evans (@scarybeasts) from google about some of those conclusion,
   >so I thought I'd expand a bit on them.
   >Does ECC protect you? Maybe not. While it will correct single bit
   flips
   >most of the time, it won't protect when multiple bits flip at once.
    Not exactly.  Generally, ECC with enough correction bits will at least
   detect all double-bit errors, although it will not correct those
   errors.  And I can't say for sure how generally this is in use, but I
   think a competently-designed ECC system will use the regular refresh
   cycles to "sweep" for correctable single-bit errors, and correct
   virtually all of them, before they turn into double-bit errors.
   >The hacker may be able to achieve this with enough tries. Remember:
   the
   >hacker's code can keep retrying this until it succeeds, even if that
   >takes hours.
   However, the profusion of corrected single-bit can be used to alert,
   and uncorrectable double-bit errors will probably cause  a system
   exception that will inform the system operator that something is going
   on.
   Remember, it is likely that different manufacturer's DRAM designs might
   differ in sensitivity to rowhammer (or other deliberate failure mode)
   by a factor of 10:1, 100:1, or even 1000:1.   The word can, and will,
   quickly get out what manufacturers sensitivity is, and the market will
   quickly result in improvement for designs and thus, new systems.
              Jim Bell

References

   1. http://blog.erratasec.com/2015/03/some-notes-on-dram-rowhammer.html