Last month, our post Are your rankings suffering from bad links? discussed the emergence of "link removal" campaigns (and even service providers) stemming from unnatural link warnings many webmasters received from Google.
The article mentioned that Google would likely release a disavow tool through which webmasters could report sources of questionable backlinks that webmasters don't want to be associated with.
Well, that tool is now here.
if you'd like the details from Google's Matt Cutts' mouth, here's the video announcement:
Remember, most folks don't need to use this tool (Dr. Pete from SEOmoz has a good explanation on this). If you believe you've been the target of "negative SEO" by a competitor or have hired a sketchy SEO in the past and your rankings appear to have been affected by recent Google updates, the disavow tool is a way you can signal to Google you reject these links pointing to you.
1. Try to work with the webmaster first. This is a directive, not a way to force Google into disavowing the links. Google has an override if it believes the links should be counted. (This may work in your favor if Google believes these are "good" links). Working with webmasters will get you a faster and more guaranteed result. Failing that, use the disavow tool.
2. Understand it will take several weeks for changes to be in effect. So make sure you submit the domains you want to submit in your file - ammendments will put you further back in the queue.
3. If you haven't already, double up your disavow efforts with Bing, as submitting to Google does not affect Bing.