Responsibility of ISPs for the ecosystem?

If you like Scott Chaney's suggestion he made at ISSE this week called Collective Defense - Applying Public Health Models to the Internet he raised very good points about the different roles the participants in the Internet Health Ecosystem have to play. Into that, the following article fits in fairly nicely: Comcast to notify subscribers with infected PCs.

What is your view? How far do ISPs have to go? How far shall they go? Shall they allow access to the Internet fi they know that your PCs is infected by a bot? If you are spreading malware?

Roger