Malicious Office (OOXML) / .XLSM — malware analysis report

Static analysis result for SHA-256 98b3fa8ad7143d6b…

MALICIOUS

Office (OOXML) / .XLSM

37.1 KB Created: 2021-01-20 10:44:11 UTC Authoring application: 16.0300
MD5: 54825e5a9b5da2c6d3e71155680a2c4d SHA-1: 98e7e3c303a0a6010b6c2bd1bbd64688eb8753a3 SHA-256: 98b3fa8ad7143d6bfb754aeca00ded8ffe5789d7e4360f51841801906f5e5551
270 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File T1105 Ingress Tool Transfer

This XLSM file contains Excel 4.0 macros that leverage the `URLDownloadToFileA` function to download a second-stage payload. The use of `RETURN()` in the XLM macro sheet and the presence of VBA code indicate a multi-stage infection process. The document body appears to be obfuscated or encrypted, preventing a direct analysis of its lure, but the macro behavior is clear.

Heuristics 7

  • URLDownloadToFile in VBA critical OLE_VBA_DOWNLOAD
    URLDownloadToFile in VBA
  • VBA ActiveX event runs worksheet-decoded XLM formulas critical OLE_VBA_ACTIVEX_XLM_CELL_STAGER
    VBA code attached to an ActiveX/UserForm event reconstructs formula text from worksheet constants using Split/Replace/Mid or character shifting, then executes it through ExecuteExcel4Macro or Run. This is a high-confidence malware stager that hides XLM formula execution in sheet cells; it is not a document-parser CVE.
  • Excel 4.0 macro sheet (2 sheet(s)) critical OOXML_XLM_MACROSHEET
    Spreadsheet contains an Excel 4.0 (XLM) macro sheet — XLM was a major Office malware vector during 2020-2022 and evaded many VBA-focused controls before Microsoft tightened XLM defaults. Even legitimate XLM use is rare in modern workbooks.
  • Dangerous XLM formula APIs: RETURN critical OOXML_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet uses formula APIs that call directly into Win32 (=CALL/=EXEC/=REGISTER/=FORMULA). These are the primitives used to download payloads, write files, and start processes from an XLM macro without invoking VBA.
  • VBA project inside OOXML medium OOXML_VBA
    Document contains vbaProject.bin — VBA macros present
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 3 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction
  • 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/spreadsheetml/2006/main
    • http://schemas.microsoft.com/office/excel/2006/main
    • http://schemas.openxmlformats.org/officeDocument/2006/relationships
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac

Extracted artifacts 5

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
868fd66cdff8e0f13d33adc8f5340c9ec7e4b6f53af837434be549e349188d98		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3111 bytes
vbaProject_00.bin
19832f2f9c20338e85a6020ce270b510e341c053f0f6e3bc83c246286e2aece1		 vba-project OOXML VBA project: xl/vbaProject.bin 23040 bytes
emf_00.emf
5a6ad5dd29dac89ddf7d058b243b6caa122a0c6fac2b9fb5f853fd49e47d4d5e		 ooxml-emf OOXML EMF part: xl/media/image1.emf 2352 bytes
xlm_sheet_00.xml
9539834b2f3ce98fb433bfd6ed41a922c8c3639a3b33fff2777ac5b056bb166a		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1174 bytes
xlm_sheet_01.xml
863373286637fadab1fdf1d4e10af1ecebec7c55dd00032186a44b7b0f1e07c1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 977 bytes

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