A click-fraud campaign has been launched using a new dangerous TDL-4 malware variant which has claimed some 280,000 victims.
The malware TDL-4 rose to infamy in 2011 when researchers discovered it supported a botnet of more than four million infected computers.
The latest version of the malware uses a domain-generation algorithm (DGA) in which the infected machines create thousands of domain names daily to hide command-and-control infrastructure.
Victims were caught in a money-making campaign where they were redirected from legitimate ads to URLs where attackers earn revenue off the traffic.
The malware variant emerged in May according to researchers at Damballa Labs, and had infected up to 30,000 machines in the past week.
Victims were usually unaware of the attack and researchers at Damballa and Georgia Tech Information Security Center did not know what types of fradulent ads were used.
“We are in the process of further analysing the ad campaign,” Damballa academic sciences director Manos Antonakakis said. “We have several people working to define what [attackers] are actually doing.”
More than 40 Fortune 500 companies are among the victims infected by the TDL-4 variant, as well as government agencies and ISP networks. Damballa also pinpointed 85 servers, hosted primarily in Russia, Romania and the Netherlands, that were linked to the botnet.
The attacks were centralised within the US, Germany and Britan, Antonakakis said.
The company described TDL4 as a multipurpose launching pad for other malware which could have other unknown features.