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Thousands of U.S. Devices Infected With New Gameover Zeus Variant: Report

Researchers at Bitdefender have been monitoring two new Gameover Zeus variants spotted in the wild and found that most of the computers they have infected are located in the United States and Ukraine.

Researchers at Bitdefender have been monitoring two new Gameover Zeus variants spotted in the wild and found that most of the computers they have infected are located in the United States and Ukraine.

The Gameover Zeus botnet was disrupted in June as a result of a takedown operation in which various law enforcement agencies and private sector companies took part. However, in mid-July, researchers spotted a new Trojan largely based on Gameover Zeus.

The new threat uses a domain generation algorithm (DGA) that’s similar to the old one, but the generated domain names are not related to the old botnet. Furthermore, this piece of malware doesn’t use a P2P infrastructure and instead relies on a technique called Fast Flux to hide malware delivery and phishing sites.

Bitdefender says each of the two variants it has analyzed use a different DGA. One of them generates roughly 1,000 domains per day, and the other one 10,000 domains per day, with each of the domains active for only one day.

Bitdefender Antimalware Research Manager Dragos Gavrilut says there aren’t any major differences between the two Gameover Zeus variants except for the DGAs. Their functionality is almost identical and there are similarities at string level as well, the expert told SecurityWeek.

In order to determine the geographical distribution of victims, Bitdefender sinkholed five domains for five days for each of the two botnets. For one of the botnets, researchers identified a total of 5.907 unique IPs that made contact with the sinkholed domains, 4.936 of which (83.7%) are from the United States. This confirms the findings of Denmark-based CSIS Security, which reported on August 3 that most “Gameover v3” infections were in the U.S.

Infections have also been spotted in India (195), Singapore (76), Japan (62), Germany (44), the United Kingdom (42), Russia (41), China (28), Turkey (26) and Mexico (25).

As for the other botnet, it doesn’t focus on the U.S., but on Ukraine and Belarus. These two countries account for 3.046 (70.7%) of infections, being followed by Turkey (244), Azerbaijan (222), Kazakhstan (118), Russia (88), Kyrgyzstan (83), Indonesia (60), Moldova (57) and Germany (55).

Bitdefender noted that while a large number of domains have been registered for the botnet that mainly targets the United States, the second botnet, whose victims are mostly in Ukraine and Belarus, doesn’t appear to be in use since no domains have been registered for it.

“However, the botnet could find itself with a new master anytime,” Bitdefender Labs experts noted in a blog post.

As far as the old Gameover Zeus botnet is concerned, Gavrilut pointed out that since the Zeus souce code was leaked in 2011, it’s not an easy task to determine if someone is trying to resurrect an old botnet or if they’re trying to create a new one. However, in this case, based on the their totally different geographic repartition and DGA code differences, it’s more likely that this is a new campaign rather than a resurrection of an old botnet, he said.

According to Dell SecureWorks, the Gameover ZeuS was the most prevalent piece of banking malware detected in 2013.

Written By

Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.

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