How we use spam reports

Google Webmaster Tools not only help us communicate with webmasters, but also provide a channel for you to inform us about spam sites you find online. Thanks to you, we’ve received many spam reports that have helped us improve search quality by showing more relevant, useful sites in our results.It's easy to submit a spam report via either of two channels, authenticated and unauthenticated. We give a higher priority to the reports that are submitted through an authenticated channel such as Webmaster Tools. Or you can submit unauthenticated reports. Since the unauthenticated reports are reported anonymously, we may give it lower priority to process.Here's how a spam report submitted from Webmaster Tools is processed:
We evaluate the spam report
We take spam reports very seriously, and we have dedicated staff to timely process reports.
We primarily evaluate spam reports in reference to our webmaster guidelines. We determine whether we agree or disagree with the user's report.
A spam site commonly uses illicit techniques to mislead search engines to (mis)lead users to certain websites. The Webmaster Guidelines cover most (but not all) common forms of behavior that we consider deceptive or manipulative. We suggest you review our webmaster guidelines listed in our Webmaster Help Center. These will help you create a search-engine friendly website that both Google and users would view as spam-free. There are cases where we disagree with the spam report's evaluation, and those reports are then disregarded. The confirmed reports are forwarded to our engineering teams.We take action on confirmed spam reports
We take action on many confirmed spam sites, either manually and/or algorithmically. Furthermore, the extent of our action is dependent on the severity of the violation -- a confirmed spam report doesn't necessarily mean the entire site will be removed from the index.Taking action on spam by improving our algorithmsIt's most efficient for us to combat spam through our algorithms. We use spam reports about one site to create algorithmic improvements detecting spam in all sites similar to the report. We then extensively test our changes before we push our new code into production. This engineering process takes time. When people ask the question "Why haven't you penalized the spam site I've reported?", if we confirmed their spam report, then it's likely that we're working, or will be working, on an algorithmic solution.Taking manual action on a spam siteWe may also take manual action on confirmed spam sites. This process is obviously much faster, but it's not as robust a method to improve our search quality as the algorithmic approach.We can contact webmasters to correct their site
If we believe that a reported spam site is in violation of the webmaster guidelines but is otherwise legitimate, we may try to contact the webmaster to correct their site. We contact webmasters via email and, if they have a verified site in Webmaster Tools, we can also send them a note through the Message Center. Our goal is to deliver the most relevant results to users. We hope that our users and webmasters keep reporting spam sites, as it helps us to improve our algorithms and improve search quality. If you have questions about what's spam, visit our Help Center or post your question in our discussion group. And, of course, if you find a spam site, please let us know!