An attack is anything that makes it take less than a brute force effort (of 2^80 operations). A 2^63 effort is really expensive in 2007. But by 2015 computation was maybe 2^5 times cheaper and there was a 2^5 cheaper attack.
I believe that this breakthrough could be quite a bit bigger because it's changing the costs from exponential to polynomial and so speedup is likely a much bigger change.
I believe that this breakthrough could be quite a bit bigger because it's changing the costs from exponential to polynomial and so speedup is likely a much bigger change.