Water Sigbin, also known as the 8220 Gang, is actively targeting Oracle WebLogic servers to deploy cryptocurrency miners. This threat actor exploits vulnerabilities CVE-2017-3506 and CVE-2023-21839 to gain initial access to the servers. Once access is achieved, they utilize PowerShell scripts to initiate the deployment of their malware. The use of fileless execution techniques allows the malware to run solely in memory, significantly reducing the likelihood of detection by traditional disk-based security mechanisms.
The attack begins with the deployment of a PowerShell script that decodes a Base64-encoded payload. This payload is dropped as an executable file named wireguard2-3.exe, which impersonates the legitimate WireGuard VPN application to avoid detection. The first-stage loader, wireguard2-3.exe, decrypts and maps a second-stage payload, which it executes in memory. This sophisticated approach helps the malware to evade both user scrutiny and antivirus software.
The second-stage payload is a DLL file named Zxpus.dll, which is injected into memory using reflective DLL injection. This DLL acts as another loader, retrieving a binary named Vewijfiv from its resources. The binary is then decrypted using AES encryption and decompressed with GZip, before being deserialized to reveal the loader’s configuration. This configuration includes details necessary for creating a process and the encrypted next-stage payload.
To further complicate detection and analysis, Water Sigbin employs .Net Reactor, a .NET code protection software, to protect all their payloads. This software obfuscates the code, incorporates anti-debugging techniques, and makes reverse engineering extremely difficult for defenders. By utilizing these advanced techniques, Water Sigbin ensures that their cryptocurrency-mining malware can operate effectively while remaining hidden from traditional security measures.
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