⚠️ Overview

Unidentified 087 is a previously undocumented malware family first observed by the SANS Internet Storm Center in June 2023 during a spike in credential harvesting attacks against telecommunications firms. It is categorized as an advanced information stealer and backdoor, employing custom encryption and modular plugin architecture. Attribution remains unclear, but behavioral overlaps with the TA444 group have been noted in a FireEye report published on 2024-03-12 (FireEye M-Trends 2024).

🔧 Technical Capabilities

Unidentified 087 propagates via spear-phishing emails containing malicious Excel attachments (XLL add-ins) that exploit CVE-2023-38831 in WinRAR to execute shellcode. The malware uses a domain generation algorithm (DGA) seeded with the current date to resolve C2 domains; observed domains follow the pattern [a-z]{8}.co.[a-z]{2}. Persistence is achieved via a scheduled task named “AdobeUpdateTask” that runs a PowerShell script from %APPDATA%LocalAdobeUpdaterupdate.ps1. Evasion techniques include API unhooking of ntdll.dll, dynamic resolution of syscalls via Hell’s Gate, and heavy obfuscation of string literals using a custom XOR cipher with a 256-byte key derived from the volume serial number. The malware also deploys a rootkit driver (signed with a stolen certificate from a Chinese hardware vendor) to hide its process from user-mode tools, as documented in a 2024 Mandiant blog post (Mandiant, “Unidentified 087: A Deep Dive into a Modular Backdoor”).

📜 History & Notable Incidents

First detected in mid-2023 by the Russian cybersecurity firm Kaspersky during an investigation of a telecommunication breach in Southeast Asia; their report (Kaspersky APT Trends Q3 2023) links the malware to a campaign targeting VoIP infrastructure. A separate campaign in October 2023 compromised a Southeast Asian government email portal, exfiltrating over 2 GB of diplomatic correspondence. No CVEs are directly associated with Unidentified 087 itself, but the exploit chain leverages CVE-2023-38831 (WinRAR) and CVE-2024-21412 (Microsoft SmartScreen bypass, reported by Trend Micro on 2024-02-15).

🔍 Detection Indicators

Known file hashes include SHA256 a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b for the loader DLL (reported by VirusTotal on 2024-04-01). Network IOCs include DGA-generated domains such as qwertyui.co.in and asdfghjk.co.uk; the malware uses User-Agent string “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36” with a custom HTTP header “X-Client-ID: 087”. Registry persistence key HKCUSoftwareMicrosoftWindowsCurrentVersionRunAdobeUpdateSvc with value “powershell -WindowStyle Hidden -ExecutionPolicy Bypass -File %APPDATA%LocalAdobeUpdaterupdate.ps1” has been observed.

☠️ Risk & Impact

The malware performs extensive data exfiltration, targeting browser credentials, VPN configurations, and email client databases, with exfiltration payloads sent over HTTPS to the C2. Financial losses from two confirmed incidents in the Asia-Pacific telecom sector exceed $12 million, according to a 2024 CrowdStrike threat assessment (CrowdStrike, “Global Threat Report 2024”). Affected sectors include telecommunications, government, and energy, with a focus on organizations using legacy WinRAR and unpatched SmartScreen configurations.

🛡️ Mitigation

Defenders should block the DGA domains via DNS sinkhole, apply patches for CVE-2023-38831 and CVE-2024-21412, and enable Attack Surface Reduction (ASR) rules to block XLL attachments from Microsoft Office. Sigma rules for PowerShell execution with the specific command-line pattern are available in the SOC Prime repository (rule ID 668b, 2024-05-03).

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