OSX DoK Malware linked to Operation Emmental used to target Swiss Banks again

Pierluigi Paganini July 10, 2017

Crooks behind the Operation Emmental hacking campaign have started targeting the Swiss banks using a variant of the DoK Mac OS X malware.

In July 2014, malware researchers at Trend Micro published a report on the hacking campaign “Operation Emmental” that was targeting Swiss bank accounts whit a multi-faceted attack that allowed crooks to bypass two factor authentication implemented by the financial organization to protect its customers.

According to the experts, the Operation Emmental has been around since at least 2012.

The experts dubbed the campaign “Operation Emmental” because of the numerous holes in the security implemented by the Swiss banks, exactly like the popular Swiss Emmental cheese.

The hackers used a malware which was able to intercept SMS tokens used to authorize operations and change domain name system settings to hijack victims to rogue bank websites, which were a replica of legitimate ones, used for phishing attacks.

The threat actors targeted bank customers’ accounts in different countries, including in Switzerland, Austria, Japan and Sweden. Investigators suspected that Russian-speaking individuals were responsible for the Operation Emmental due clues discovered in the source code analyzed.

The hackers behind the Operation Emmental have continued to improve their malicious codes. The hackers used on Android malware and a Windows banking Trojan tracked as Retefe and WERDLOD.

The novelty in the operation of the group is represented by the usage of a new variant of the Dok malware in a new wave of attacks against the Swiss banks.

The malicious code is delivered via email, once the DOK malware infects a macOS system, it gains administrative privileges and installs a new root certificate. The root certificate allows the malicious code to intercept all victim’s communications, including SSL encrypted traffic.

According to researchers at Trend Micro, the malware variant tracked as OSX_DOK.C is configured to hijack traffic only if the victim’s external IP is located in Switzerland.  OSX_DOK.C redirects users to bogus login pages for the financial organizations whose domain is included in a hardcoded list.

“The OSX_DOK malware (Detected by Trend Micro as OSX_DOK. C)  showcases sophisticated features such as certificate abuse and security software evasion that affects machines using Apple’s OSX operating system.” reads the analysis published by Trend Micro.

The Dok sample detected by Trend Micro was considered by the malware researchers the Mac version of Retefe/WERDLOD.

“While WERDLOD and OSX_DOK.C use different codes (since they target different operating systems), they have similar proxy settings and script formats.”

“Comparing it to OSX_DOK.C, we can see that it uses the same script format” Trend Micro researchers said in a blog post.

“Given the connection between WERDLOD and OSX_DOK.C, it is reasonable to assume that the latter is also a part of the Operational Emmental campaign,” 

Operation Emmental osx dok

The researchers observed that the latest versions of the Dok malware leverage a bug in the Ultimate Packer for Executables (UPX) tool to pack the Trojan and avoid detection.

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Pierluigi Paganini 

(Security Affairs – Dok Malware, Operation Emmental)

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