A sophisticated group of cybercriminals has stolen over $25 million by hacking into the infrastructure of numerous financial institutions in Russia and former Soviet Union countries, as well as into point-of-sale systems belonging to U.S. and European retailers.Researchers from Russian cybercrime investigations firm Group-IB and Dutch security firm Fox-IT have dubbed the cybercriminal group Anunak, after the primary malware program in its toolset.Unlike most cybercrime operations where attackers target the customers of financial institutions, the Anunak group targeted the institutions themselves, compromising their internal networks, workstations and servers. This access allowed them to transfer funds to accounts under their control and in some cases even to compromise ATMs, which they then used to withdraw money fraudulently."Since 2013 they have successfully gained access to networks of more than 50 Russian banks and 5 payment systems, and 2 of these institutions were deprived of their banking license," Group-IB said in a report released Monday. "To date the total amount of theft is over 1 billion rubles (about 25 million dollars), most of it has been stolen in the second half of 2014."The Anunak attackers start by infecting the computers of regular employees with malware and then move laterally inside the network by compromising servers and active domain accounts. The group uses network scanners, keyloggers, password crackers, SSH backdoors, remote control programs and often the Metasploit penetration testing framework.However, their primary tool is a computer Trojan dubbed Anunak, based on Carberp, a malware program designed to steal online banking credentials and whose source code was leaked online in June 2013. The Group-IB researchers believe that some members of the Anunak group were previously members of the Carberp gang which split up in 2013 following internal conflicts.The attackers use several methods to infect computers with the Anunak Trojan. These include drive-by downloads through exploit kits (the group is believed to have injected malicious code in the php.net site in 2013 to attack its visitors), spoofed emails with malicious attachments that claim to be sent by the Central Bank of the Russian Federation and installation through other malware programs as part of pay-per-install agreements."The criminal group keeps in touch with several owners of large botnets that massively distribute their malware," the Group-IB researchers said. "The attackers buy from these botnet owners the information about IP addresses of computers where the botnet owners have installed malware and then check whether the IP addresses belong to financial and government institutions. If the malware is in the subnet of interest, the attackers pay the large botnet owner for installation of their target malware."Starting in the second quarter of 2014, the Anunak group also targeted retailers in the U.S., Australia and Europe with the goal of infecting point-of-sale (POS) terminals with malware that can steal payment card data during transactions.At least 16 possible breaches have been identified at retail organizations -- 12 of them in the U.S. -- and theft of credit card data was confirmed in three of those cases, the researchers said in their report. The group also compromised computers at three U.S.-based PR and media organizations, possibly with the intention of obtaining trading advantages on the stock market, they said."We have no evidence of compromises against banks in Western Europe or United States, but it should be noted that the attackers methods could be utilized against banks outside of Russia as well," the researchers warned.