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

Static analysis result for SHA-256 7802f1db1091eee3…

MALICIOUS

Office (OOXML) / .XLSM

234.5 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: f03f74c039e033aa41093d9fbb802743 SHA-1: b951b65b881b2724433e9520ef788da3f2febd71 SHA-256: 7802f1db1091eee3d5fbb096a605abcb52d6359cc8274cc1449fa65244254a3f
250 Risk Score

Malware Insights

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

The sample is an Excel macro-enabled spreadsheet (XLSM) containing Excel 4.0 macros. Critical heuristics indicate the use of dangerous XLM functions like FOPEN, FWRITE, FCLOSE, EXEC, and REGISTER, which are used to download and execute payloads. The macro sheet reconstructs the path "C:\ProgramData\DbfsB.sct" and uses FOPEN to open this file. It then writes data to this file, likely a script, and subsequently uses the EXEC function to run it. This indicates a downloader or dropper functionality.

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
42f27a25e8a92156ae61759feca2863de93a7661d110d582d96a0cab5b314ca4		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 729033 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.