Botnet fraud costs advertisers $6 million a month in false clicks

"Security researchers have discovered a botnet they have dubbed "Chameleon" which they calculate is costing display advertisers around $6m (£3.9m) per month by falsely viewing billions of pages and adverts on about 200 sites owned by a small group of publishers.
The discovery points to widespread fraud in which adverts are clicked among networks of sites to generate money for sites and ad networks – though it is still unclear whether it is one or more publishers, or one or more ad networks which supply ads to the sites, which are to blame for the fraud.
Spider.io, a security group which previously pointed out that a flaw in internet Explorer was being exploited by advertising companies to track users, says that the botnet consists of at least 120,000 subverted Windows machines, 95% of them located inside the US."

Source:  The Guardian, 19th March 2013