Google took a stringent measure to clean up all the malware on its SERP’s by blocking and annihilating some 11 million odd sites, belonging to the co.cc domains.
Google describes Co.cc domain (owned by a Korean company) as a “freehost” which offers free or really cheap priced domains often in bulks. So spammers are naturally attracted to have their low-quality sites hosted there.
When Google performed a scan on the co.cc domain it revealed that the domain contained a very high percentage of ‘spammy’ sites. This prompted the search giant to ban the entire .co.cc sub-domain rather than penalizing each site individually, resulting in all sites being removed from its search results.
In the words of Google’s John Mu:
If we see a very large fraction of sites on a specific free host be spammy or low-quality, we do reserve the right to take action on the free host as a whole. I think most savvy search/SEO folks would understand this completely, but I figure it’s better to over-communicate than under-communicate.
Definitely this action by Google has been welcomed by a majority of the webmasters in taking back control of the SERP’s. For the website’s who were hosted on the co.cc domains – I guess free is not always good.
If your site has been impacted in this clear out, then I suggest you submit a reconsideration request to Google for review. Good luck!