Last year researchers from security vendor Kaspersky Lab were called in to investigate unusual thefts from 29 banks and other organizations located in Russia, leading to the discovery of three new sophisticated attack campaigns. Their findings were presented Monday during the company's annual Security Analyst Summit.
One group of attackers is using a modular malware program known as Metel or Corkow to infect computer systems belonging to banks and to reverse ATM transactions. During a single night, the gang stole millions of rubles from a Russian bank using this hard-to-detect transaction rollback trick.
The Metel attackers start off by sending spear phishing emails with malicious links to the employees of banks and other financial institutions. Once they compromise computers in those organizations, they move laterally inside the networks to identify and gain access to the systems that control transactions.
Once this is achieved, they automate the rollback of ATM transactions for particular debit cards issued by the institution. During the night, the attackers drive around various cities and withdraw money from the ATMs of other banks. However, in the card issuing bank's systems the transactions are automatically reversed so the account balances never change.
The Kaspersky researchers said that they discovered the Metel malware on computers belonging to 30 financial institutions from Russia. However, they believe that the group's activities are far more widespread and could affect financial organizations from around the world.
A second group that also targets banks and financial institutions uses a malware program dubbed GCMAN, which is distributed using emails with malicious executable RAR archives and which masquerade as Microsoft Word documents.
Similarly to some cyberespionage groups, the GCMAN attackers use legitimate system administration and penetration testing tools like Putty, VNC and Meterpreter for lateral movement inside networks. The group identifies servers that handle financial transactions and creates cron jobs (scheduled tasks) to automate transfers to multiple e-currency services, typically during weekends. In one case, the Kaspersky researchers found scripts that initiated transactions at a rate of $200 per minute.
The GCMAN group also stands out because of its patience. In one incident, it waited a year and a half from the initial point of compromise until it started siphoning money. During that time its members probed 70 internal hosts, compromised 56 accounts and used 139 different IP addresses to do it, mainly associated with Tor exit nodes and compromised home routers.
As with Metel, the Kaspersky researchers only identified GCMAN victims in Russia, specifically three financial institutions. However, it's likely that the group's reach extends beyond the country.
The third group is not new, but is one that previously went silent for about five months after being exposed in February 2015. Until that time, the cybercime gang had used a custom malware program called Carbanak to steal millions of dollars from hundreds of financial institutions in at least 30 countries.
The group has returned with a new version of the malware -- Carbanak 2.0 -- and has started targeting budgeting and accounting departments in non-financial organizations as well.
"In one remarkable case, the Carbanak 2.0 gang used its access to a financial institution that stores information about shareholders to change the ownership details of a large company," the Kaspersky researchers said in a blog post. "The information was modified to name a money mule as a shareholder of the company, displaying their IDs. It’s unclear how they wanted to make use of this information in future."
Kaspersky Lab has released indicators of compromise for the tools used by all three groups so that organizations around the world can scan their own networks for potential compromise.