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

Static analysis result for SHA-256 d1a785afd164bb2c…

MALICIOUS

Office (OOXML) / .XLSX

138.0 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 2d4c10d7fd6a3bbc1d52eb2e27c15d0c SHA-1: 85d6b9b0aa0e192a6141f718bb9b76cc4121fb1f SHA-256: d1a785afd164bb2c5d932ada9920879984a7cc2b26ed8512828fda39b26dd2d1
250 Risk Score

Malware Insights

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

The file is an Excel 4.0 macro-enabled spreadsheet. Heuristics indicate the use of dangerous XLM functions like FOPEN and EXEC, which are commonly used to download and execute payloads. The macro attempts to construct a path to 'C:\ProgramData\' and uses functions that suggest it will write a file and execute it. The ClamAV signature 'Xls.Downloader.Dridex122100-9913248-0' further supports its role as a downloader, likely for the Dridex banking trojan.

Heuristics 6

  • 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.
  • Excel 4.0 Auto_Open defined name critical OOXML_XLM_AUTOOPEN_DEFINEDNAME
    Workbook defines _xlnm.Auto_Open or _xlnm.Auto_Close while containing an XLM macro sheet. This is the OOXML/XLSB auto-execution shape for Excel 4.0 macros.
  • Dangerous XLM formula APIs: FOPEN, FWRITE, EXEC, 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.
  • ClamAV: Xls.Downloader.Dridex122100-9913248-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Dridex122100-9913248-0
  • 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
31566444ce0216c29041b2b2b0ca6bfd0a3be8c410bb35db5c04e028d4464d98		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 5238 bytes

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