The takedown of the Rustock botnet earlier this year has had ripple effects throughout the malware and spam ecosystems. Researchers say that the Harnig pay-per-install malware is making a comeback, sans Rustock, however. The most likely reason is that there has been a tremendous amount of attention focused on Rustock in the last six months, from the media, researchers and law enforcement. The botnet was at the core of a huge spam empire and also was a key component of the DDoS and attack landscape in general.
Source: https://threatpost.com/harnig-botnet-returns-without-rustock-081111/75529/