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

Static analysis result for SHA-256 9185532b309a8681…

MALICIOUS

Office (OOXML) / .XLSM

307.9 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 9bc8137da8d29b6792f036a3fd4aedbb SHA-1: 9c941c9a1e2e439eaae618a99b39f967510abd1d SHA-256: 9185532b309a86813f3fedc1ad02d0c1a36ab9d1f09db28337080032b094ba0e
250 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous functions like FOPEN and EXEC to write and execute a script file located at 'C:\ProgramData\MjQBPNBkBq.sct'. This indicates a downloader or dropper functionality, aiming to execute a second-stage payload. The use of Excel 4.0 macros and the specific file path suggest a custom or less common 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
365cef2653486e6e7dc86d5e09ca546a7e984534111fc6ec6a071a8e6f9f9522		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1598349 bytes

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