For SEP-2010, the number is pretty standard and similar to previous months. Out of those top 1 million sites, around 3 thousand got blacklisted last month. Out of the top 100k, more than 300 got blacklisted by Google.
Those are the top 50k sites that got flagged and their respective ranking (You can get the full list here):
What is interesting is the number of “security” related sites registered as “.co.cc”. All of them were used to spread malware, especially the “Fake AV” (some of them even ranked in the top 100k):
More than 50% were infected through the latest OpenX vulnerability. Another interesting point is that more than 75% of the sites that got hacked were using outdated software (either Joomla, WordPress, OpenX, etc). If you are a site owner, this is a reminder to keep your site updated.
We will post more details in future posts. If you have any question or comment about it, let us know.