🦠 Malware Analysis
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🎯 Threat Intelligence
Executive summary: Recent investigations reveal a repeatable campaign where attackers abuse ConnectWise ScreenConnect installers hosted in open directories to distribute AsyncRAT and a custom PowerShell RAT.
The campaign combines trusted RMM footprints, ClickOnce pivots and payload containers that evade signature-based detection.
Technical details:
• Observed payloads include AsyncRAT and a bespoke PowerShell RAT delivered alongside trojanized ScreenConnect installers.
• Infrastructure enumeration identified multiple hosts (examples:
176.65.139.119, 45.74.16.71, 164.68.120.30) and repeated file names such as logs.ldk, logs.idk, logs.idr ranging from ~60 KB to 3 MB.
• Execution techniques show two distinct code paths: in-memory .NET Assembly.Load for AV‑guarded environments and native injection via libPK.dll::Execute otherwise.
• Persistence mechanisms include scheduled tasks named SystemInstallTask and 3losh with aggressive intervals (every 2–10 minutes).
• Network/C2 tradecraft spans common ports (21/80/111/443) and high ephemeral ranges (30,000–60,000), often wrapped in TLS.
🔹 Attack Chain Analysis
• Initial Access / Phishing: ClickOnce pivots (e.g., police.html → galusa.ac.mz → dual.saltuta.com) delivering a launcher from /Bin/ paths.
• Download: Trojanized ScreenConnect installer retrieved from open directory hosting.
• Execution: Dual paths — Assembly.Load into memory or libPK.dll native injection.
• Persistence: Creation of scheduled tasks with short recurrence.
• C2 / Telemetry: AsyncRAT beaconing over standard and ephemeral ports with TLS.
Impact & analysis: Abusing legitimate RMM installers introduces supply‑chain‑like risk; trusted installer footprints lower detection fidelity and enable long dwell times. Fresh or repackaged containers missing from VirusTotal indicate active re‑use and rapid churn.
Detection guidance:
• Monitor for creation of scheduled tasks named SystemInstallTask/3losh and unusual recurrence intervals.
• Alert on processes performing .NET Assembly.Load from nonstandard locations and on native DLLs named libPK.dll performing injection-like behaviors.
• Hunt for open directory listings exposing logs.ldk|logs.idk|logs.idr and ClickOnce /Bin/ URL patterns.
Mitigations:
• Harden RMM deployment processes, restrict installer hosting and validate installer hashes.
• Block or monitor suspicious open directory access and implement strict egress controls for ephemeral port ranges.
• Enforce application allowlisting and endpoint behavioral detections for in-memory assembly loads and DLL injection.
🔹 AsyncRAT #ScreenConnect #ClickOnce #RMM #C2
🔗 Source: https://hunt.io/blog/asyncrat-screenconnect-open-directory-campaigns