Analysis released today from Arbor Networks reveals that cybercriminals powering GameOver Zeus, that was taken down by law enforcement in early June, have restored the botnet with at the least 12,353 unique IP addresses globally. Arbor’s numbers originate from five sinkholes it controls, and information gathered occasionally between July 18 and July 29.
“The steady growth of newGOZ demonstrates the resilience of the attackers to keep their botnet active,” stated Dave Loftus, security analyst at Arbor Networks. “While previous efforts to disrupt the botnet have been successful, these disruptions are usually only temporary. Until law enforcement can successfully prosecute the individuals behind the botnet, we expect the growth of newGOZ to continue well into the future.”
The takedown, coordinated between the FBI and Europol, included the seizure of servers and domain names that interrupted not just GameOver Zeus but authorities said the botnet was utilized to deliver CryptoLocker ransomware.
GameOver Zeus, a variant of the controversial Zeus banking Trojan. As opposed to it’s big brother. GameOver till recently used a decentralized peer to peer architecture rendering it difficult to interrupt. In a P2P architecture, commands are sent back and forth from individual bots instead of from a command and control server.
GameOver Zeus, like various other banking malware, is employed in fraud schemes and to steal banking credentials from the victims’ computers. Soon after the takedown, experts at Seculert discovered the newGOZ variant which left behind peer-to-peer communication for an updated domain generation algorithm. The DGA swiftly ramped up new bots from 1,000 per week, to 1,000 a day on average, as outlined by CTO Aviv Raff.
“It uses a domain generation algorithm and a technique known as fast-fluxing to check into the criminal infrastructure. Since this DGA takes the current date and a randomly selected starting seed to create a domain name, we can predict which domains will be used in the future. With this in mind, we were able to register the domains before the attackers did, which allowed us to redirect the malware traffic to our servers to track the growth of the botnet,” Loftus said. “Once the domains were registered, the newGOZ infections checked into our servers as we expected. We were able to log the unique number of IP addresses associated with the infections and determine the locations that have been hit the hardest.”
“Our sinkhole data reinforces steady growth of new Gameover Zeus since we started tracking the botnet,” Loftus stated. Experts at Malcovery mentioned in mid-July how the Cutwail botnet began distributing newGOZ via spam campaigns. “Our sinkhole data provides a first look at how successful these spam campaigns have been. Between July 21-25, we observed a 1,879 percent increase, confirming that the cybercriminals are actively rebuilding their botnet from scratch.”
The majority of the victims are typically in the United States and India, with ISPs, telecommunications and education markets supplying the most victims.