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

Static analysis result for SHA-256 09cceb619174c99d…

MALICIOUS

Office (OOXML) / .XLSM

37.1 KB Created: 2021-01-20 10:44:11 UTC Authoring application: 16.0300
MD5: 28e9c78dcffb4a80c7bcfcd818791940 SHA-1: 0f239865c9e2bdd64d2017c7d26cac19dc7d3cde SHA-256: 09cceb619174c99d026734f860f26cda0107af31b9153a9f7d6613c86fd57772
270 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

This XLSM file contains Excel 4.0 macros and VBA code. The VBA code utilizes the URLDownloadToFileA function, indicating an attempt to download a second-stage payload from a remote source. The presence of dangerous XLM formula APIs like RETURN further supports the execution of arbitrary code. The document body appears to be obfuscated or encoded, preventing a direct analysis of its lure.

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 a VBA project — 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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