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

Static analysis result for SHA-256 c170b070cc70ccb4…

MALICIOUS

Office (OOXML) / .XLSM

304.8 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 90f9986b219bcd08b55cc909a10697a1 SHA-1: 95eefe41fd92c4aa08b6a77f29e23bc52537b0c7 SHA-256: c170b070cc70ccb4879a9b7915f990275a8befad2a01a2fa94cb582d51c25105
250 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1059.003 Windows Command Shell

This XLSM file contains Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET and OOXML_XLM_AUTOOPEN_DEFINEDNAME heuristics. The macros utilize dangerous functions like FOPEN, FWRITE, FCLOSE, EXEC, and REGISTER, which are known primitives for downloading and executing payloads. Specifically, the macro attempts to write to and execute a script file located at 'C:\ProgramData\MTXXXmA.sct'. The ClamAV detection further confirms its malicious nature as a downloader.

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, FCLOSE, EXEC, HALT 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.Trojan-a0425f7f2000faff-a0425f7f2000faff-9950268-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Trojan-a0425f7f2000faff-a0425f7f2000faff-9950268-0
  • 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
1ec7cf0a28f2bf0688273822befe2e15aac06399925090d3fe470f1a6d370319		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1575448 bytes

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