Security Experts:

"Callisto" Cyberspies Target Europe, South Caucasus

F-Secure on Thursday published a report detailing the activities of Callisto, a threat actor whose primary goal appears to be intelligence gathering from entities interested in European foreign and security policy.

According to F-Secure, which hasn’t found any links between this and other known threat actors, the Callisto group has been active since at least October 2015. The hackers have been observed targeting various individuals and organizations in Eastern Europe and the South Caucasus region, which encompases Georgia, Armenia and Azerbaijan.

In late 2015, when F-Secure started tracking Callisto, the group had sent out highly targeted Gmail phishing emails. Some of the messages were sent to personal email addresses, suggesting that the attackers had previously conducted reconnaissance. Experts believe the hackers managed to hijack some accounts and used them to send phishing emails to other targets.

In early 2016, the cyberspies sent spear-phishing emails carrying malicious documents to military and government officials, think tank employees and journalists. F-Secure is aware of the malicious emails sent to these individuals, but it’s unclear if the targets actually installed the malware on their systems.

The Word documents sent to targets embedded a piece of malware as an object, eliminating the need for using exploits. If recipients clicked on the document and allowed the package content to run when prompted, the malware would be executed.

The malware has been identified as Scout, one of the tools available in the RCS Galileo platform of Italian spyware maker Hacking Team. The company was hacked back in 2015 and many of its tools were leaked online. Researchers determined that the Callisto group used the installers that had been leaked at the time, rather than relying on the Galileo source code.

The Scout malware has been described as a light backdoor that can be used for reconnaissance and to install other malware on the infected system.

F-Secure’s analysis revealed that the Callisto group’s infrastructure had been linked to servers hosting stores that sell controlled substances, which suggests a possible cybercrime connection. Experts also discovered links between the infrastructure used by the threat actor and countries such as Russia, Ukraine and China.

“A cyber crime group with ties to a nation state, such as acting on behalf of or for the benefit of a government agency, is one potential explanation,” researchers said in their report. “However, we do not believe it is possible to make any definitive assertions regarding the nature or affiliation of the Callisto Group based on the currently available information.”

While F-Secure has not seen any Callisto attacks involving malware for more than a year, the security firm says the group is still active, with new phishing infrastructure set up every week.

It’s worth pointing out that the Russia-linked threat actor dubbed APT28, Pawn Storm and Fancy Bear has also been known to target entities in Eastern Europe and the Caucasus region.

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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.