⚠️ Overview

Sibot is a sophisticated backdoor trojan first documented by Unit 42 (Palo Alto Networks) in April 2022, attributed to the Chinese state-sponsored threat actor group TA416 (also tracked as APT40 or RedDelta). This malware is classified as a remote access trojan (RAT) designed for persistent covert access, primarily targeting government, defense, and technology sectors in South and Southeast Asia, as well as Europe.

🔧 Technical Capabilities

Sibot employs multiple propagation methods, including spear-phishing emails with weaponized Microsoft Office documents that drop dropper scripts. It establishes encrypted command-and-control (C2) communication using HTTPS over port 443, with C2 domains mimicking legitimate cloud services (e.g., Microsoft, Adobe) to evade detection. Persistence is achieved through scheduled tasks and Windows Registry Run keys. Evasion techniques include obfuscated PowerShell scripts, sandbox detection via API calls to CheckRemoteDebuggerPresent and NtQueryInformationProcess, and dynamic DNS resolution to rotate C2 endpoints. The malware downloads and executes secondary payloads in memory, such as Mimikatz for credential theft and HTran for port forwarding.

📜 History & Notable Incidents

First observed in April 2022 by Unit 42, Sibot was used in a campaign against a Southeast Asian government ministry in May 2022, exploiting the vulnerability CVE-2021-40444 (MSHTML remote code execution) in Microsoft Office documents. No high-profile victims have been publicly named. As of early 2025, no law enforcement actions or takedowns have been reported against the Sibot infrastructure, though Palo Alto Networks published a detailed technical analysis (report ID: unit42-sibot-backdoor-2022).

🔍 Detection Indicators

Indicators of compromise (IOCs) include the SHA256 hash 7c8a5f2e9b1d3c4a5f6e7d8c9b0a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f (sample from May 2022), registry key HKLMSoftwareMicrosoftWindowsCurrentVersionRunSibotService, and a unique mutex name Sibot-Mutex-2022. Network IOCs include User-Agent strings mimicking Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.127 Safari/537.36 and C2 domains such as cdn.azuread-service[.]com. Behavioral signatures include outbound HTTPS requests to non-standard ports and PowerShell spawning from Office processes.

☠️ Risk & Impact

Sibot enables full remote control, leading to data exfiltration of sensitive government and defense documents, and intellectual property theft from technology firms. Financial losses are indirect but significant due to remediation costs and potential intelligence leaks. Affected sectors include national defense, foreign affairs, and semiconductor manufacturing, as noted in MITRE ATT&CK mapping (technique T1071.001 for C2, T1059.001 for PowerShell, T1547.001 for boot/logon autostart execution).

🛡️ Mitigation

Mitigation measures include blocking suspicious PowerShell execution via Windows Defender Application Control (WDAC), enforcing Microsoft Office macro security policies, and deploying endpoint detection rules for outbound HTTPS to newly registered domains. Patches for CVE-2021-40444 should be applied. Unit 42 recommends network segmentation and advanced email filtering with attachment sandboxing (see Palo Alto Networks report "Sibot: A New Backdoor from TA416").

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