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

Static analysis result for SHA-256 c7e6848fd6368151…

MALICIOUS

Office (OOXML) / .XLSM

33.5 KB Created: 2021-01-21 13:13:53 UTC Authoring application: 16.0300
MD5: a52a88ae97dd408d38d98c9aa7f81142 SHA-1: 234b65bc42a077c98c61a8eb4870d41e0039013e SHA-256: c7e6848fd63681514d6dad3032e358a257dde3aa1cd3b349306283356bca2608
270 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros that leverage the `URLDownloadToFileA` API to download a second-stage payload. The presence of `OLE_VBA_ACTIVEX_XLM_CELL_STAGER` and `OOXML_XLM_DANGEROUS_FN` heuristics indicates the use of advanced techniques to execute arbitrary code. The `RETURN()` function in the XLM macro sheet is a strong indicator of malicious intent, likely to download and execute a payload.

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 (1 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 4

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
46f567b19043f6a0f4ba5e2dc1f72be5c4b27d2599ea59b80993c345bea7ae3e		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3518 bytes
vbaProject_00.bin
d9e9e5e9eb5674e4763704bf07c9cac95aed70c929fdbd0e88bb7475d93ab232		 vba-project OOXML VBA project: xl/vbaProject.bin 24576 bytes
emf_00.emf
a1d83b13577385965d59963af5c15deca6de97aaa0c0c0446ebb4f46ee340309		 ooxml-emf OOXML EMF part: xl/media/image1.emf 1408 bytes
xlm_sheet_00.xml
77b101f1e72af643575b161f01e7d34912c3215c39ee9e2096163568b84f2d9f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1545 bytes

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