Inside The Million-Machine Clickfraud Botnet

Online advertising is a multi-billion dollar business mostly ran by Google, Yahoo or Bing via AdSense-like programs. The current generation of clickbots such as the Redirector.Paco Trojan have taken abuse to a whole new level, burning through companies’ advertising budget at an unprecedented pace.
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The malware’s objective is to redirect all traffic performed when using a popular search engine (such as Google, Yahoo or Bing) and replace the results with others obtained from a Google custom search. The goal is to help cyber-criminals earn money from the AdSense program.

https://labs.bitdefender.com/2016/05/inside-the-million-machine-clickfraud-botnet/