⚠️ Overview

Cmoon is a backdoor malware family first discovered in 2020 by Trend Micro, associated with the Chinese advanced persistent threat (APT) group tracked as C‑Moon (MITRE ATT&CK group ID G0126). It is categorized as a trojanized remote access tool (RAT) designed for targeted cyber espionage, primarily against government, diplomatic, and defense entities in Southeast Asia. The group is believed to operate under state sponsorship, with activities noted by Palo Alto Networks Unit 42 and other threat intelligence vendors.

🔧 Technical Capabilities

Written in C++, Cmoon employs DLL side‑loading by dropping a malicious DLL (often named version.dll or msdoh.dll) alongside a legitimate signed executable (e.g., a Microsoft or Intel binary) to achieve execution without triggering user‑account control. Persistence is achieved via a Windows service or a Registry Run key under HKCUSoftwareMicrosoftWindowsCurrentVersionRuncmoon. The C2 infrastructure uses HTTPS with custom encryption and mimics legitimate domains (e.g., using .xyz or .ml TLDs) to evade network detection. Evasion techniques include encrypting payloads with RC4 or XOR, base64 encoding of configuration data, and process injection into svchost.exe or explorer.exe. Propagation is primarily through spear‑phishing emails containing malicious Office documents that exploit known vulnerabilities (e.g., CVE‑2017‑0199 or CVE‑2018‑0802) to drop the initial loader.

📜 History & Notable Incidents

Cmoon was first publicly documented in a 2020 Trend Micro report detailing an operation against embassies in Myanmar, Laos, and Cambodia. In 2021, Palo Alto Networks described a follow‑up campaign targeting South Korean defense contractors and Indian government agencies. No law enforcement actions have been reported against the group. The malware is linked to the C‑Moon APT group, which also deploys other families such as PlugX and Korplug in overlapping campaigns.

🔍 Detection Indicators

Known file hashes include SHA256 values from VirusTotal samples such as e5a11c… (notable for the 'cmoon' mutex) and 70b6c… (from Unit 42 reports). Behavioral signatures include the creation of a mutex named GlobalCmoonMutex or MSDOH_MUTEX, and dropped files in %APPDATA%Microsoft. Network indicators: C2 domains ending in .xyz or .ml, IP addresses in the 45.77.0.0/16 range (hosted on Vultr or Choopa), and HTTP requests with a User‑Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 variant that includes a hard‑coded Referer: http://www.google.com.

☠️ Risk & Impact

Cmoon provides attackers with full remote access, including keylogging, screen capture, file exfiltration, and command execution, enabling long‑term intelligence gathering. Victims have suffered data theft of classified diplomatic communications and defense blueprints. The primary affected sectors are government ministries, embassies, and defense contractors, with financial losses primarily attributed to the cost of incident response and intellectual property loss rather than direct ransom demands.

🛡️ Mitigation

Defenders should deploy endpoint detection and response (EDR) rules that monitor for DLL side‑loading of common legitimate binaries, block the known C2 IP ranges and domains via network filtering, and apply patches for Microsoft Office vulnerabilities (CVE‑2017‑0199, CVE‑2018‑0802). Additionally, restrict execution of unsigned binaries in user‑writable paths and enable application whitelisting on critical hosts.

ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the malware listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.