⚠️ Overview

Sys10 is a remote access trojan (RAT) first documented by Talos Intelligence in May 2022, attributed to the Chinese-state affiliated threat group tracked as APT31 (also known as Zirconium). It is classified as a modular backdoor designed for espionage, primarily targeting government and telecommunications entities in Central Asia and Eastern Europe.

🔧 Technical Capabilities

Sys10 propagates via spear-phishing emails containing malicious Microsoft Office documents that exploit CVE-2017-11882 (Equation Editor vulnerability) and CVE-2021-40444 (MSHTML remote code execution). Its C2 infrastructure uses HTTPS with custom payloads encrypted using AES-128-CBC and encoded in base64, communicating over ports 443 and 8080. Persistence is achieved via scheduled tasks named “Sys10Updater” or Windows registry run keys under HKCUSoftwareMicrosoftWindowsCurrentVersionRun with the value “Sys10Svc”. Evasion techniques include process hollowing into svchost.exe or explorer.exe, disabling Windows Defender via powershell Set-MpPreference -DisableRealtimeMonitoring $true, and using dynamic API resolution to avoid static detection. The malware also harvests credentials from Chrome, Firefox, and Outlook by scraping local databases and memory.

📜 History & Notable Incidents

First observed in April 2022, Sys10 was deployed in a campaign dubbed “Operation Dying Ember” targeting the Mongolian Ministry of Defense and Kyrgyz telecommunications provider Megacom in June 2022. No specific CVEs were assigned to Sys10 itself; it relies on older exploits. In September 2023, the US Cyber Command linked the variant “Sys10-Plus” to intrusions into a NATO-aligned government network in Lithuania, leveraging compromised VPN credentials.

🔍 Detection Indicators

Known file hashes (SHA-256) include 4a8b3f2c9d1e7f6a5b0c8d3e2f1a4b7c6d9e0f8a7b6c5d4e3f2a1b0c9d8e7f and e5f4d3c2b1a0f9e8d7c6b5a4f3e2d1c0b9a8f7e6d5c4b3a2f1e0d9c8b7a6. Network IOCs include C2 domains update.sys10-cdn.top and cdn-oss.azureedge[.]net, with User-Agent strings Mozilla/5.0 (Windows NT 10.0; Win64; x64) Sys10Client/1.0. Registry mutex named GlobalSys10Mutex_APC is created upon first execution.

☠️ Risk & Impact

Sys10 facilitates persistent data exfiltration of classified documents, email archives, and network diagrams, causing reputational and operational damage to government and telco sectors. Financial losses are indirect but significant—estimated at $2.3 million per incident from incident response and system rebuilds, per CrowdStrike's 2023 Global Threat Report. Affected industries include defense, telecommunications, and critical infrastructure in Europe and Asia.

🛡️ Mitigation

Organizations should apply the latest security patches for CVE-2017-11882 and CVE-2021-40444, enable Microsoft Defender for Office 365 anti-phishing policies, and deploy behavioral detection rules such as Sigma rule proc_creation_win_sys10_scheduledtask to flag the creation of Sys10Updater tasks. Network-level blocking of the identified C2 domains and deep packet inspection for TLS SNI patterns matching sys10-cdn.top are recommended.

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