ESET Research Uncovers New Cyberespionage Group Worok Targeting Companies, Govts Mostly in Asia

• ESET researchers have discovered a previously unknown cyberespionage group that they named Worok.
• Worok has attacked various high-profile companies from the telecommunications, banking, maritime, energy, military, government, and public sectors. The targets are located mostly in Asia, but also in the Middle East and Africa.
• Worok develops its own tools and leverages existing tools to compromise its targets. The group has used the infamous ProxyShell vulnerabilities to gain initial access in some cases. Its PowerShell backdoor PowHeartBeat has various capabilities, including command/process execution and uploading and downloading files.

yESET researchers recently discovered targeted attacks that used undocumented tools against various high-profile companies and local governments mostly in Asia, but also in the Middle East and Africa. These attacks were conducted by a previously unknown cyberespionage group that ESET has named Worok. According to ESET telemetry, Worok has been active since at least 2020 and continues to be active today. Among the targets were companies from the telecommunications, banking, maritime, energy, military, government, and public sectors. Worok used the infamous ProxyShell vulnerabilities to gain initial access in some cases.

"We believe the malware operators are after information from their victims because they focus on high-profile entities in Asia and Africa, targeting various sectors, both private and public, but with a specific emphasis on government entities,” says ESET researcher Thibaut Passilly who discovered Worok.

Back in late 2020, Worok was targeting governments and companies in multiple countries, specifically:

• A telecommunications company in East Asia
• A bank in Central Asia
• A maritime industry company in Southeast Asia
• A government entity in the Middle East
• A private company in southern Africa

There was a significant break in observed operations from May 2021 to January 2022, but Worok activity returned in February 2022, targeting:

• An energy company in Central Asia
• A public sector entity in Southeast Asia

Worok is a cyberespionage group that develops its own tools and leverages existing tools to compromise its targets. The group’s custom toolset includes two loaders, CLRLoad and PNGLoad, and a backdoor, PowHeartBeat.

Technical Analysis

While the majority of initial accesses are unknown, in some cases through 2021 and 2022 we have seen exploits used against the ProxyShell vulnerabilities. In such cases, typically webshells have been uploaded after exploiting these vulnerabilities, in order to provide persistence in the victim’s network. Then the operators used various implants to gain further capabilities.

Once access had been acquired, the operators deployed multiple, publicly available tools for reconnaissance, including Mimikatz, EarthWorm, ReGeorg, and NBTscan, and then deployed their custom implants: a first-stage loader, followed by a second stage .NET loader (PNGLoad).

Unfortunately, the ESET team have not able to retrieve any of the final payloads. In 2021, the first-stage loader was a CLR assembly (CLRLoad), while in 2022 it has been replaced, in most cases, by a full-featured PowerShell backdoor (PowHeartBeat) – both execution chains are depicted in Figure 2. These three tools are described in detail in the following subsections.

Worok compromise chains

CLRLoad is a first-stage loader that was used in 2021, but in 2022 was replaced, in most cases, by PowHeartBeat. PNGLoad is a second-stage loader that uses steganography to reconstruct malicious payloads hidden in PNG images.

PowHeartBeat is a full-featured backdoor written in PowerShell, obfuscated using various techniques such as compression, encoding, and encryption. This backdoor has various capabilities, including command/process execution and file manipulation. For example, it is capable of uploading files to and downloading files from compromised machines; returning file information such as the path, length, creation time, access times, and content to the command and control server; and deleting, renaming, and moving files.

“While our visibility at this stage is limited, we hope that putting the spotlight on this group will encourage other researchers to share information about this group,” adds Passilly.
For more technical information about Worok, check out the blogpost “Worok: the big picture” on WeLiveSecurity. Make sure to follow ESET Research on Twitter for the latest news from ESET Research.

Visual heatmap of the targeted regions and verticals 

Map of the targeted regions and verticals

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