The stealthy ZeroAccess botnet commands a zombie army of more than one million machines, according to new research.
A study by Sophos published last week reveals that the latest version of the malware, which is designed for either click fraud or Bitcoin mining, has infected more than 9 million machines over its lifetime. The infected population accessible to unknown botherders at any one time is estimated at around one million. Machines are lost to the botnet through clean-up action by users. But that's only a small concern to cybercriminals, who are raking in plenty of revenue through the zombie network they control.
"If running at maximum capacity, the ZeroAccess botnet is capable of making a staggering amount of money: in excess of $100,000 a day," Sophos estimates.
ZeroAccess first appeared on the scene around two years ago, in November 2010. Previous versions of the malware used URLs associated with the infamous Russian Business Network to spread hard-to-clean and stealthy rootkit functionality.
The latest variant of the malware differs from the previous versions in dropping some of the rootkit-style features. Even so, a white paper by James Wyke of Sophos on the botnet, "The ZeroAccess Botnet - Mining and fraud for massive financial gain, concludes that ZeroAcess is a persistent threat that is likely to hang around as an irritant for years to come.
"Although the network is peer-to-peer based, centralised servers are used to record installations and keep tabs on active infections. The authors take great pains to disguise network traffic to these servers as innocuous, ordinary traffic," Wyke concludes.
"Many aspects of ZeroAccess display the authors’ fondness [for] fall-back options and backups. There is always more than one way for ZeroAccess to start up on an infected machine; the droppers phone home in two different ways during installation; each time specific functionality needs a server address there is usually a backup address if the first cannot be reached."
A map of ZeroAccess botnet infections in Western Europe and the US, compiled by F-Secure, can be found here. ®