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

Static analysis result for SHA-256 bd0a70575336c7c2…

MALICIOUS

Office (OOXML) / .XLSM

57.8 KB Created: 2021-01-27 09:16:15 UTC Authoring application: 16.0300
MD5: db3d5929c4a2d0bb150b60f09a2aa120 SHA-1: 4090d6e7e53645df72ac2f844e1030c1e8d9eda5 SHA-256: bd0a70575336c7c295d763de9b56f4c7f4e5a8cccf7dc65798fc0dab71d129d0
250 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The critical heuristic 'OOXML_XLM_DANGEROUS_FN' indicates the use of dangerous XLM formula APIs like RETURN, which can be used to download and execute payloads. The VBA script also contains a declaration for URLDownloadToFileA, further supporting the payload download functionality. The presence of a hidden sheet suggests an attempt to conceal malicious activity.

Heuristics 7

  • 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.
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_Open macro
  • 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
977f2d6cd2e75d8aa4f847fb1a819beb1ae65eef3a2e9a0aeaa895cadd496880		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2779 bytes
vbaProject_00.bin
ce575b8164d74b90498fa9dcd92e6826f68e1b789e863f7a5c895b9d0c6b9361		 vba-project OOXML VBA project: xl/vbaProject.bin 19968 bytes
xlm_sheet_00.xml
80f6f0ca9cead0c0a655de5d7db416bfc33bc1e27df33d7a656bb4f465e941e5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1095 bytes

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