The Russian Federal Security Service (FSB) arrested eight hackers who allegedly stole US$4.5 million in the last quarter alone using an online banking Trojan, security analyst firm Group-IB announced on Tuesday.

The group comprised seven Russians and one person in Abkhazia, an independent republic in a territory claimed by Georgia. The group was first noticed in the beginning of 2010 and used a Trojan to compromise systems, said Michael Sandee,security specialist at the Dutch security firm Fox IT, who assisted in many stages of the investigation.

Apart from Fox IT, Group-IB and the Russian Federal Security Service (FSB), the Russian Ministry of the Interior (MVD) also worked on the investigation. The group of eight hackers was arrested on Monday, said Aleksey Kuzmin, head of Group-IB's U.S. office.

The criminals used the Caberb Trojan, aimed at wide range of Windows operating systems -- Windows 200 through Windows 7 -- according to Sandee. "That Trojan gathers an alarming amount of data," he explained in a phone interview. Caberb logged a wide variety of passwords and login data once it installed itself on a system.

Caberb would nestle itself in computers using various browser vulnerabilities, including Java and Flash browser plugin vulnerabilities. Once inside, the Trojan would launch a so-called man-in-the-browser attack. Caberb placed itself in the browser, and was used to run a protocol sniffer, detecting passwords and login credentials. The Trojan was also able to manipulate traffic to serve phishing sites without the user knowing he was visiting one.

Together with the Caberb Trojan, Rdpdor malware was used to manipulate systems. Rdpor is a program that is able to establish a full Remote Desktop Protocol (RDP), Sandee said, which allowed the criminals to see what the users sees on the screen, or even take over the whole machine if the criminal wanted to.

When the group obtained login credentials for online banking sites they were used for fraudulent transactions that were sent to a specially prepared account. The scammers hacked popular news media websites and online stores, among other methods, to spread the malicious software, said Group-IB in a press release.

The eight hackers mainly targeted electronic banking systems in Russia, Eastern Europe and The Netherlands, Sandee said. They were active in The Netherlands until November 2010 and then shifted their focus to Eastern Europe, mainly because there are six authentication systems in use in that area while in The Netherlands every bank uses its own authentication system.

"The Eastern European authentication systems are not bad," said Sandee, but emphasized that the small number of systems gave the cyber criminals "more value for their money."

Both Group-IB and Fox IT noted that it is fairly uncommon to be able to arrest an entire criminal chain. In typical actions against cyber criminals, only part of a group gets arrested, Sandee noted. Some people, like the leaders, are often not arrested because they are difficult to identify, he said. Usually the criminal who operates the botnet is the easiest to find.

The effort to take down the whole group is why the investigation took about a year and a half to complete. Group-IB said that the head of the group was first identified in January 2010. The investigators put a vast amount of effort in documenting his activities, which was complicated because he was constantly on the move, traveling often outside of the Russian Federation.

Loek covers all things tech for the IDG News Service. Follow him on Twitter at @loekessers or email tips and comments to [email protected]