A common monetization method used by malware distributors is to secretly replace legitimate ads that get loaded on the machine (such as Google's) with their own.
Doing this on every single web page visited by that machine for the rest of its existence, and multiplying that by hundreds of thousands of other infected machines out there, and multiplying THAT by the dozens of different black hat groups doing this simultaneously, it adds up to a lot of lost money for Google.
A common monetization method used by malware distributors is to secretly replace legitimate ads that get loaded on the machine (such as Google's) with their own.
Doing this on every single web page visited by that machine for the rest of its existence, and multiplying that by hundreds of thousands of other infected machines out there, and multiplying THAT by the dozens of different black hat groups doing this simultaneously, it adds up to a lot of lost money for Google.