Win.Dropper.Zusy — Office (OLE) malware analysis

Static analysis result for SHA-256 a63b14427599f2b4…

MALICIOUS

Office (OLE)

915.5 KB Created: 2021-07-12 12:27:00
MD5: 3e3b1a040d3429770f05bb38020a08a5 SHA-1: d268baceb92b02e889522cabeeea38f0f5dad725 SHA-256: a63b14427599f2b4cef5b5cc496c9c5b70064e93bf160adc1e15677233335a8b
642 Risk Score

Malware Insights

Win.Dropper.Zusy · confidence 95%

MITRE ATT&CK
T1203 Exploitation for Client Execution T1059.005 Visual Basic

The sample is a malicious Microsoft Word document that exploits CVE-2007-3899 to achieve code execution. It contains VBA macros that attempt to download and execute a second-stage payload, identified as 'ier.dll', into the user's template directory. The embedded executable and the ClamAV detection further confirm its malicious nature as a dropper.

Heuristics 17

  • CVE-2007-3899 — Microsoft Word malformed string memory corruption critical CVE likely CVE_2007_3899
    Word OLE document has the MS07-060 malformed-string exploit shape: a Word 97-family FIB points to a malformed DOP/string-table region with an abnormal INT_MAX run, inflated text counters, and exploit payload or Mdropper.Z campaign evidence.
  • Office EPRINT stream contains EMF object high CVE related OLE_EPRINT_EMF_OBJECT
    OLE ObjectPool contains an EPRINT stream with EMF data. This is rare in normal documents and is CVE-2007-3893/MS07-046-family evidence when paired with Office exploit payload anomalies, but the malformed EMF record is not proven by this rule alone.
  • OLE with Ole10Native — possible CVE-2026-21514 exploitation high CVE likely CVE_2026_21514
    Document contains a Word OLE object with Ole10Native plus executable, PE, or risky remote-link indicators. CVE-2026-21514 exploits OLE metadata validation; this stronger structure is treated as likely exploitation.
  • Embedded PE executable critical OLE_EMBEDDED_EXE
    MZ/PE header found inside document — possible embedded executable
  • ClamAV: Win.Dropper.Zusy-9878669-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Dropper.Zusy-9878669-0
  • ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV
    ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
  • Reference to ShellExecute API high SC_STR_SHELLEXEC
    Reference to ShellExecute API
  • Reference to LoadLibrary API high SC_STR_LOADLIBRARY
    Reference to LoadLibrary API
  • Reference to GetProcAddress API high SC_STR_GETPROCADDRESS
    Reference to GetProcAddress API
  • Document_Open macro high OLE_VBA_DOCOPEN
    Document_Open macro
  • Ole10Native package carries executable/script file type high OFFICE_PACKAGE_RISKY_FILE
    OLE Package displayName or fullPath ends in an executable or script-capable extension. Even without UI extension spoofing, embedding a runnable payload inside an Office document is a high-risk delivery pattern.
  • VBA p-code auto-exec with execution tokens high OLE_VBA_PCODE_AUTOEXEC_EXEC
    Compiled VBA/cache stream contains an auto-execution token together with shell/download/object-execution tokens. This catches p-code-only or source-extraction-failure macro documents where visible source is unavailable.
  • Reference to VirtualAlloc API medium SC_STR_VIRTUALALLOC
    Reference to VirtualAlloc API
  • Reference to VirtualProtect API medium SC_STR_VIRTUALPROTECT
    Reference to VirtualProtect API
  • Excel 4.0 (XLM) macro sheet present medium OLE_XLM_AUTOOPEN
    Workbook contains an Excel 4.0 macro sheet sub-stream — XLM is rarely seen in modern legitimate workbooks and was a major Office malware vector during 2020-2022.
  • VBA macros detected medium OLE_VBA_MACROS
    Document contains VBA macro code
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://schemas.openxmlformats.org/drawingml/2006/main

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
50290679413fa5de936f4cd413e05327aac82cb3378c3f3da70508a5d09e862d		 vba-macro oletools.olevba.extract_macros (decoded VBA source) 3154 bytes
embedded_office_0008ec6e.exe
7d4b859f0a819e005a0f057aba26ce7f359a39bfa0fab46238b65e5617893ada		 embedded-pe Office MZ+PE at offset 0x8EC6E 352658 bytes
Detection
ClamAV: Win.Dropper.Zusy-9878669-0
Obfuscation or payload: unlikely
ole10native_00.bin
d397a7766a9eab547f064cb810bccba8c5ea45a4cce3e1c8b4d9cf9c0e0195ca		 ole-package OLE Ole10Native stream: ObjectPool/_1687573113/Ole10Native 311596 bytes
Detection
ClamAV: Win.Dropper.Zusy-9878669-0
Obfuscation or payload: unlikely

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