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

Static analysis result for SHA-256 7ae43f4cc722e36e…

MALICIOUS

Office (OOXML) / .XLSM

35.0 KB Created: 2021-03-01 13:56:52 UTC Authoring application: Microsoft Excel 16.0300
MD5: c974f73e438cdd56984019d3865ff90b SHA-1: 4a220d6065e17de7900d4e18b534b730229ac65c SHA-256: 7ae43f4cc722e36e2950f07b312a85499d6fca2d8b1aad7b358b7a836daa47a2
210 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 both VBA macros and Excel 4.0 macros. The VBA code utilizes the URLDownloadToFileA function, indicating an attempt to download a second-stage payload from a remote source. The presence of Excel 4.0 macros, specifically using the RETURN() function, further supports the execution of arbitrary code. The document body appears to be heavily obfuscated or corrupted, making its specific lure difficult to determine, but the technical indicators strongly suggest a downloader functionality.

Heuristics 6

  • URLDownloadToFile in VBA critical OLE_VBA_DOWNLOAD
    URLDownloadToFile in VBA
  • 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 1 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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
90e1029031be36f6f97a4d72c7f1ec04b43723f2c7594055be366751595e6e45		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2722 bytes
vbaProject_00.bin
fda8be90d354b50c53685a7776f4cca1bd13fd13015649f86eab62c72ab12b11		 vba-project OOXML VBA project: xl/vbaProject.bin 20480 bytes
xlm_sheet_00.xml
a39fa49e98e85e4cbb4d343028f030569c7f524f7caef108df9b23443dd6e131		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 968 bytes

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