From Google Ideas.
This is an interesting overview of the general traffic and what they are beginning to do to identify what it is and how to clean it up, not just for the general public, but also for activists and those whose voices would be suppressed.
The issue is more complex than it seems, I think Microsoft has been addressing botnets and malware for sometime with its security updates, often in the list of updates you will see something call “Malicious software removal tool“, which I assume is their windows update approach (this is conjecture on my part, I would certainly do it this way). The above video outlines a Google ISP level approach where they look at the types of data that are being transmitted, how much of it is from malware ..etc.
Being able to filter out of the internet Denial of Service attacks and SPAM networks at the ISP level would make everyones pages load faster. Make the world a little safe, dealing with how people get malware which is mostly silent and unknown to the user.