The Google Search quality team said to webmasters :
Google spokesman Mark Jansen said in an email :
It’s part of our ongoing mission to be transparent with webmasters and do our bit to help prevent spam. In fact this isn’t a new phenomenon, we communicate very openly with webmasters and always have done.
Google’s anti-malware campaigns can have a big impact. Last July Google excluded more than 11 million URLs from the “co.cc” domain, because they were regularly used by cybercriminals to spread antivirus programs and conduct drive-by attacks. Google explained in a blog post at the time that some bulk providers could host more than 50,000 malware domains, and that it could flag whole bulk domains in severe cases.