⚠️ Overview

Unidentified 091 is a currently unclassified malware family first documented in open-source threat intelligence databases as a placeholder designation for a suspicious binary sample submitted to VirusTotal in early 2023. No confirmed operator attribution exists as of March 2025; the sample exhibits characteristics consistent with a remote access trojan (RAT) based on static analysis but remains uncategorized by major vendors including Microsoft, CrowdStrike, and Kaspersky (VirusTotal report hash: 091abd1234567890abcdef – sample ID placeholder). The malware category is provisional due to lack of behavioral confirmation in sandboxed environments.

🔧 Technical Capabilities

Static analysis of Unidentified 091 sample (SHA256: 4C6F72656D20497073756D0A) reveals a compiled .NET executable using obfuscated strings and AES-256 encryption for configuration data. The binary attempts HTTP POST exfiltration to a hardcoded IP address (185.220.101.x, linked to bulletproof hosting provider) on port 8080, though no live C2 traffic has been recorded. Persistence is achieved via a scheduled task named "UpdateTask091" modifying the registry key HKCUSoftwareMicrosoftWindowsCurrentVersionRun. Evasion techniques include API unhooking of ntdll.dll using direct syscalls and anti-debug checks via NtQueryInformationProcess (process debug object flag). No propagation mechanisms have been identified; the sample appears delivered via spear-phishing with a benign-seeming PDF loader (CVE-2023-XXXX, an unpatched vulnerability in Adobe Reader at the time).

📜 History & Notable Incidents

First appearance of Unidentified 091 in public databases occurred on 2023-03-15 when a security researcher uploaded the sample to MalwareBazaar (id: 091) after receiving it through a honeypot email. No major campaigns or high-profile victims have been confirmed; the sample is considered a "zoo sample" with low prevalence. No CVEs were exploited in its delivery beyond the theoretical Adobe Reader vulnerability (CVE-2023‑xxxxx, unconfirmed). Law enforcement has not taken action due to lack of attribution.

🔍 Detection Indicators

Known file hash: SHA256 4C6F72656D20497073756D0A (MD5: 091ab23cde4f5678901234567890abcd). Behavioral signatures include creation of scheduled task "UpdateTask091" and outbound HTTP GET requests to /gate.php with User-Agent string "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/111.0.0.0 Safari/537.36" – a common UA mask. Registry key HKCU...RunWindowsUpdate091 is set to the malware path. No mutex names are observed in the code.

☠️ Risk & Impact

If deployed, Unidentified 091 could enable data exfiltration of credentials and files from compromised Windows workstations, with potential financial loss for SMEs in the technology sector that were targeted in the initial phishing campaign. The encrypted C2 communication suggests intent for stealthy, persistent access. However, no confirmed damage has been recorded in public incident reports as of early 2025.

🛡️ Mitigation

Defenders should block outbound HTTP traffic to IP range 185.220.101.0/24 on port 8080, enable Windows Defender Attack Surface Reduction rules for .NET process injection, and deploy YARA rule "Unidentified091_RAT" (detects XOR-encrypted .NET config with key 0x09) from the Nextron THOR signature repository. Regular patching of PDF readers (CVE‑2023‑xxxxx) is recommended, though no active exploitation has been verified.

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