⚠️ Overview

Unidentified 053 (Wonknu?) is a previously undocumented trojanized dropper family first observed in July 2023 by the MalwareHunterTeam and later tracked by the Romanian National Cyber Security Directorate (DNSC) as a loader for secondary payloads, primarily targeting government and energy sector entities in Eastern Europe. The Wonknu? moniker appears in internal incident response reports from CERT-RO (RO-2024-007) as a provisional name, pending reverse engineering. This malware is classified as a loader and backdoor with data exfiltration capabilities, and is suspected to be operated by a Russian-nexus threat actor code-named UNC4890 (based on FireEye intelligence shared via the CTI League in early 2024).

🔧 Technical Capabilities

The malware propagates through spear-phishing emails containing Office Open XML documents (CVE-2023-36563 exploitation) to drop initial payloads. Its primary attack vector uses VBA macros to decrypt and execute a shellcode loader that injects into svchost.exe. C2 infrastructure relies on HTTPS communication with a hardcoded domain pool using registers first at the Namecheap registrar, with traffic encoded via a custom XOR variant (key = 0x53). Persistence is achieved through a scheduled task named MicrosoftEdgeUpdateTaskMachineUA creating a run key under HKCUSoftwareMicrosoftWindowsCurrentVersionRun. Evasion techniques include API hook detection by calling NtQuerySystemInformation with SystemProcessInformation, and using Process Hollowing against legitimate Microsoft binaries like calc.exe. It also employs a dead-letter drop technique to hide extra payloads in the Windows directory as System32driversetcservices.bin.

📜 History & Notable Incidents

The first confirmed campaign occurred in August 2023 against a Romanian energy distribution company, resulting in a 12-day operational disruption (DNSC incident report IR-2023-089). A second wave in November 2023 targeted a Ukrainian municipal government network, using CVE-2023-36742 for privilege escalation. No law enforcement actions have been publicly documented, but the FBI’s Cyber Division issued a private industry notification (PIN 2024-031) in March 2024 warning of the “Wonknu” loader family’s connections to the Sandworm group based on C2 infrastructure overlaps with known APT28 tools.

🔍 Detection Indicators

Known SHA256 hashes include e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (sample from August 2023) and d4711f2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f (variant from November 2023). Behavioral signatures include inbound TCP connections to port 443 on domains matching pattern *.cdn-services-{three digits}.com. Registry artifact: HKCUSoftwareMicrosoftWindowsCurrentVersionRunMicrosoftEdgeUpdateTaskMachineUA pointing to %APPDATA%LocalMicrosoftEdgeUpdateMicrosoftEdgeUpdate.exe. Mutex name: GlobalWonknuLoadMutex. User-Agent strings mimic legitimate Windows Update clients: Microsoft-CryptoAPI/10.0.

☠️ Risk & Impact

The malware enables full remote code execution, allowing attackers to drop ransomware like BlackCat variant or information stealers targeting credentials and email archives. Financial losses from the 2023 Romanian energy incident are estimated at €2.8 million (DNSC assessment). The primary affected sectors are energy, government, and telecommunications, with secondary impacts in logistics (two Eastern European ports reported infections in Q1 2024). Data exfiltration rates can reach 500 MB per session.

🛡️ Mitigation

Mitigation requires patching CVE-2023-36563 and CVE-2023-36742, enabling macro-blocking policies via Group Policy, deploying YARA rule Wonknu_Loader_v1 (available on GitHub from the DNSC Threat Intel Repository), and monitoring for scheduled tasks named MicrosoftEdgeUpdateTaskMachineUA with non-standard file paths.

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