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

Static analysis result for SHA-256 f03234e69c590e38…

MALICIOUS

Office (OOXML) / .XLSM

233.8 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 0b1145386e54c133263fc6e8a9a71ed5 SHA-1: 425de0627c45d39118b4ab7e15e07fc97df1f31f SHA-256: f03234e69c590e38fb19c15c19a1b1526da18d6ea8d2634ae9fd81dbf5168b2c
250 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros. These macros utilize dangerous functions like CALL, FOPEN, FWRITE, and FCLOSE to write content to a file and potentially execute it. Specifically, the macros construct the path 'C:\ProgramData\qFnTH.sct' and write various character codes to it, likely forming a script. The use of these functions indicates an intent to download and execute a second-stage payload. The ClamAV detection further supports its malicious nature.

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
e350226587cb8975aee4c954ced024a83160fc9b59eb1709c6eb824a8c0b3115		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 687382 bytes

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