TDSS rootkit infects 1.5 million US computers in 2011 alone. Researchers from security firm Kaspersky Lab penetrate C&C servers used to control the malware’s latest version, TDL-4. If active, this number of compromised computers could make it one of the largest botnets in the world, with the US portion alone worth an estimated $250,000 (..155,000) to the underground economy. Researchers noticed a kad.dll component of the infection which appears to allow TDSs/TDL-4 to control bots using the Kad P2P file exchange network even if the primary encrypted channel has been shut down.
Source: https://thehackernews.com/2011/06/tdss-rootkit-infects-15-million-us.html