Hackers Built a Windows Backdoor Whose Entire C2 Lives Inside Microsoft 365
Antino Windows backdoor routes its entire command-and-control through Microsoft 365, using themed HTA/WSF stagers against Taiwan, Tibet, and Latin America targets.
Analysis documents the Antino Windows backdoor, whose entire C2 channel is hidden inside Microsoft 365 services. Dozens of HTA and WSF stagers use geopolitically themed lures—including CSIS Indo-Pacific, Taiwan information-warfare workshops, TPiE inauguration, Venezuela/Ukraine news, and cross-border repression seminars—to deliver a multi-stage chain. This comprises a Stage 2 JScript downloader/decryptor, encrypted JScript orchestrators, encrypted BinaryFormatter resources, TestAssembly.dll downloaders, and final slc.dll backdoors in Gen 1 and Gen 2 variants plus standalone fake installers.
- C2 traffic fully embedded in Microsoft 365 services to evade detection
- HTA/WSF stagers use geopolitical lures targeting Taiwan, Tibet, Venezuela, Ukraine
- Multi-stage chain: stager, JScript downloader, encrypted orchestrator, slc.dll backdoor
- Antino Gen 1 and Gen 2 variants plus standalone fake installers identified
- Dozens of unique SHA-256 indicators published for detection
Indicators of compromiseauto-extracted · verify before use · export allAll →
| Type | Indicator | Context |
|---|---|---|
| domain | d2nq35tel3ucuo.cloudfront.net | osdnoifnsoid[.]pages[.]dev Execution-tracking domain Domain d2nq35tel3ucuo[.]cloudfront[.]net CloudFront staging domain Domain pub-abfa7742e315485a98 |
| domain | d32tpl7xt7175h.cloudfront.net | v/VD7F3WxnOsState.dat.pgy Sideload-package component Domain d32tpl7xt7175h[.]cloudfront[.]net Downloader infrastructure overlap with UNC6384; relatio |
| domain | login.microsoftonline.com | C2; not independently evidence of compromise Service domain login.microsoftonline.com Legitimate authentication endpoint; not independently evide |
| domain | microsoft-flash.com | xp32b[.]pages[.]dev Cloudflare Pages delivery domain Domain microsoft-flash[.]com Standalone fake-installer delivery domain Domain wps-cn[. |
| domain | my-3lyt6wcp.pages.dev | 5f11f14bfe4c[.]r2[.]dev Cloudflare R2 staging domain Domain my-3lyt6wcp[.]pages[.]dev Cloudflare Pages delivery domain Domain my-qc39r814[.]p |
| domain | my-662ylt3w.pages.dev | 9r814[.]pages[.]dev Cloudflare Pages delivery domain Domain my-662ylt3w[.]pages[.]dev Cloudflare Pages delivery domain Domain my-6g16qsfe[.]p |
Full article1,274 words · extracted from cybersecuritynews.com · click to collapse
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hexadecimal identifier>[.]r2[.]devTestAssembly.dllGatherOsState.exeslc.dllOsGather.datOsState.datflashcenter_pp_ax_install_en.exeresult.ps1mshta.exesdiageng.dllsdiagnhost.execmd.exepowershell.exeItems likely to be considered in the next Cabinet meeting.T11065885611.doc.exe/antino/heartbeats/{id}.json/antino/heartbeats/<session_id>.json/antino_downloads/{file}/antino_uploads/{file}{session_id}.jsoncommand_req_[session_id]command_res_[session_id]b2b3adb0-1669-4b94-86cb-6dd682ddbea3{1F3D8AA5-9EBF-4EE4-85C2-EA40379AEDE8}C:\Windows\diagnostics\system\PCWC:\Windows\Temp\SDIAG_<GUID>%LOCALAPPDATA%\Windows GatherOSStateKit\%windir%\SysWOW64\sdiagnhost.exe 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msvc\release\deps\slc_template.pdbD:\a\antino\antino\target\x86_64-pc-windows-msvc\release\deps\antino_client_template.pdbD:\a\antino\antino\target\i686-pc-windows-msvc\release\deps\antino_client_template.pdb