APT36, also referred to as Clear Tribe, has launched a brand new malware marketing campaign that targets Indian authorities and strategic entities by abusing Home windows LNK shortcut information.
The assault begins with spear‑phishing emails that carry a ZIP archive named “On-line JLPT Examination Dec 2025.zip,” utilizing an examination discover theme to lure officers into opening the attachment.
As soon as extracted, the archive exhibits a file that seems to be a standard PDF, “On-line JLPT Examination Dec 2025.pdf,” however is in reality a shortcut file.
This shortcut makes use of a double extension trick (.pdf.lnk). Home windows hides the .lnk half, so even customers who view file extensions nonetheless see what seems like a PDF.
The file measurement is over 2 MB, which is uncommon for a shortcut and nearer to an actual PDF. Cyfirma analysts recognized that the additional measurement comes from a full PDF construction and a number of embedded pictures saved contained in the LNK to make it look extra convincing.
Cyfirma researchers famous that this marketing campaign is designed for lengthy‑time period spying, giving the attackers distant management, information theft, and surveillance options by way of a .NET‑primarily based Distant Entry Trojan (RAT).
Shortcut file properties and its irregular measurement (Supply – Cyfirma)
The malware runs in reminiscence, makes use of trusted Home windows instruments, and talks to its command‑and‑management server over encrypted channels, making it more durable for regular safety instruments to identify and hint.
An infection Mechanism and LNK Execution Chain
When the sufferer opens the pretend PDF shortcut, Home windows really launches mshta.exe from System32 and passes a distant HTA script as an argument, as a substitute of opening a doc.
Extraction of the a number of embedded pictures (Supply – Cyfirma)
Cyfirma’s evaluate of the shortcut exhibits the goal path calling a distant loader at innlive.in:-
mshta.exe ”
The HTA script runs in a hidden window, shrinks the browser body to zero, after which makes use of customized Base64 and XOR routines to decode two foremost payload blocks named ReadOnly and WriteOnly in reminiscence.
Major DLL Execution (Supply – Cyfirma)
A pattern of the JavaScript logic exhibits this sample:-
operate CDDownload(s){ /* base64 decode logic */ }
operate ProcessSignal(str,ok){ /* XOR loop */ }
var ReadOnly = USBContents(SyncDataToCD(“HxgVCQYKYhx4Z2dAdEAKRQ4bC…”));
ReadOnly weakens .NET safety checks and units the runtime, whereas WriteOnly hundreds an encrypted DLL as a RAT immediately in reminiscence. A hidden “usb” folder with usbsyn.pim seemingly holds further encrypted information for later phases.
To maintain the person calm, the HTA fetches and opens an actual JLPT examination PDF, so the entire sequence seems like regular doc viewing whereas the system is already compromised.
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