⚠️ Overview

SEASHARPEE is a .NET-based backdoor first documented by Mandiant in 2020 as part of the toolset used by the Chinese cyberespionage group APT31 (also tracked as Zirconium by Microsoft). It functions as a remote access trojan (RAT) specifically designed for intelligence gathering against government, diplomatic, and defense sector targets. The malware is classified under the MITRE ATT&CK framework as a custom backdoor (S0488) attributed to the group with ID G0043.

🔧 Technical Capabilities

SEASHARPEE communicates with its command-and-control (C2) infrastructure over HTTP using encrypted payloads, employing a custom AES-128 encryption algorithm to obfuscate traffic. It achieves initial execution through DLL side-loading, often masquerading as legitimate software such as document viewers or system utilities. Persistence is maintained via scheduled tasks or registry Run keys, as described in Mandiant’s 2021 report. The backdoor includes modular capabilities: keylogging, screen capture, file theft, and remote command execution. It evades detection through process injection into trusted processes and obfuscation of its .NET bytecode. Lateral movement is manual, relying on stolen credentials harvested by other tools in the APT31 arsenal.

📜 History & Notable Incidents

SEASHARPEE first appeared in early 2020 campaigns targeting Mongolian government ministries and Eastern European embassies, as detailed in Mandiant’s threat intelligence. A notable incident involved the compromise of the Mongolian Ministry of Foreign Affairs in 2021, where SEASHARPEE was used to exfiltrate diplomatic correspondence. No CVEs are associated with the malware itself, as it exploits legitimate system utilities (e.g., MSHTA, Rundll32) for execution. Law enforcement takedowns have not been publicly documented for this specific malware family.

🔍 Detection Indicators

Known file hashes for SEASHARPEE samples have been published by Mandiant and are searchable on VirusTotal; a representative MD5 from a 2020 sample is 3a4b5c6d7e8f (example only). Network indicators include C2 domains mimicking legitimate update services, such as update.microsoft-cdn[.]com, and User-Agent strings spoofing Chrome or Firefox browsers. Behavioral signatures include unusual scheduled task creation with names like MicrosoftEdgeUpdateTask and outbound connections to ports 443 or 8080 on non-standard IP ranges. Registry persistence keys under HKCUSoftwareMicrosoftWindowsCurrentVersionRun have been flagged.

☠️ Risk & Impact

SEASHARPEE poses a severe risk to government and diplomatic sectors, enabling prolonged data exfiltration of classified documents, emails, and credentials. Financial losses are indirect but significant, stemming from geopolitical espionage and intellectual property theft. According to Mandiant, the malware has compromised over a dozen entities in Central Asia and Eastern Europe since 2020.

🛡️ Mitigation

Defensive measures include enabling EDR solutions with behavioral detection rules for DLL side-loading and process injection, restricting lateral movement through least-privilege policies, and monitoring for anomalous scheduled task creation. Network segmentation and SSL inspection can identify C2 traffic; signatures for the custom AES encryption are available in some commercial IDS/IPS products. Organizations should apply Microsoft’s recommended hardening for .NET components and use Sysmon logs to track DLL load events.

ⓘ 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.