Robin Good: If you are curious to see how a negative SEO spammer can be tracked and uncovered, here is a good story to read.
From the original article: "Google recently updated its claims regarding the ability of other webmasters to affect your rankings via negative SEO.
While questions about the efficacy of negative SEO continue to exist, it does not seem to be slowing down the growth of what is arguably the most contemptible part of the search industry.
On July 9th, a good friend of mine reached out to me with a problem. As a very risk-averse webmaster, he constantly plunges into the numbers, especially anchor text diversity, in order to make sure his site is as penalty-proof as possible.
The latest updated data in SEOmoz's MozScape revealed a massive shift towards anchor text over optimization for several primary terms. It took only a few minutes to identify the culprit."
The rest of the article contains a detailed and illustrated story of how the author was able to backtrack the attacker(s) and how he went about searching for hints.