A joint technical alert from the DHS, the FBI, and the Treasury warning about a new ATM cash-out scheme, dubbed “FASTCash,” used by Hidden Cobra APT.

The US-CERT has released a joint technical alert from the DHS, the FBI, and the Treasury warning about a new ATM cash-out scheme, dubbed “FASTCash,” being used by the prolific North Korean APT hacking group known as Hidden Cobra (aka Lazarus Group and Guardians of Peace).

The activity of the Lazarus Group surged in 2014 and 2015, its members used mostly custom-tailored malware in their attacks and experts that investigated on the crew consider it highly sophisticated.

This threat actor has been active since at least 2009, possibly as early as 2007, and it was involved in both cyber espionage campaigns and sabotage activities aimed to destroy data and disrupt systems.

The group is considered responsible for the massive WannaCry ransomware attack, a string of SWIFT attacks in 2016, and the Sony Pictures hack.

According to the report published by the US-CERT, Hidden Cobra has been using the FASTCash technique since at least 2016, the APT group targets bank infrastructure to cash out ATMs.

Government experts analyzed 10 samples of malware involved in FASTCash attacks, state-sponsored hackers used them to compromise payment “switch application servers” within the targeted banks to facilitate fraudulent transactions.

“FASTCash schemes remotely compromise payment switch application servers within banks to facilitate fraudulent transactions. The U.S. Government assesses that HIDDEN COBRA actors will continue to use FASTCash tactics to target retail payment systems vulnerable to remote exploitation.” states the report.

“According to a trusted partner’s estimation, HIDDEN COBRA actors have stolen tens of millions of dollars. In one incident in 2017, HIDDEN COBRA actors enabled cash to be simultaneously withdrawn from ATMs located in over 30 different countries. In another incident in 2018, HIDDEN COBRA actors enabled cash to be simultaneously withdrawn from ATMs in 23 different countries.”

Switch application server communicates with the core banking system to validate user’s bank account details for a requested transaction.

HIDDEN COBRA attackers deployed legitimate scripts on compromised switch application servers to intercept and reply to financial request messages with fraudulent but legitimate-looking affirmative response messages.

Experts noticed that all of the compromised switch application servers were running unsupported IBM Advanced Interactive eXecutive (AIX) operating system versions.

At the time, the infection vector is still unknown, anyway, there are no evidence attackers successfully exploited the AIX operating system in these incidents.

“HIDDEN COBRA actors exploited the targeted systems by using their knowledge of International Standards Organization (ISO) 8583—the standard for financial transaction messaging—and other tactics.” continues the report.

“HIDDEN COBRA actors most likely deployed ISO 8583 libraries on the targeted switch application servers. Malicious threat actors use these libraries to help interpret financial request messages and properly construct fraudulent financial response messages.”

Most accounts used to initiate the transactions had a minimal activity or zero balances.

The FASTCash cash-out scheme was used to target banks in Africa and Asia, while U.S. authorities are still investigating incidents in the country that may be linked with this technique.

Experts believe APT threat actors carried out spear-phishing attacks against the bank, malicious messages used Windows executable.

The malicious code was used for lateral movements aimed at deploying malware onto the payment switch application server.

US-CERT provided mitigation recommendations for Institutions with Retail Payment Systems, including the implementation of two-factor authentication for any access to the switch application server.

Further details, including IoCs, are reported in the alert.

Pierluigi Paganini

( Security Affairs – Hidden Cobra, FastCash)

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