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

Static analysis result for SHA-256 1625bee16a2a6e37…

MALICIOUS

Office (OOXML) / .XLSM

307.6 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 5700de0858ee2f95fd05d394943f4133 SHA-1: f6af21839da3165fa58e78f67c918091de3fb7f4 SHA-256: 1625bee16a2a6e37da02eaa1f25783e2bfb0ffcc633064d347cf88de06ae1df3
250 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

This Excel macro-enabled spreadsheet (XLSM) contains critical Excel 4.0 macros, including the use of dangerous functions like FOPEN, FWRITE, FCLOSE, EXEC, and HALT. The macro code constructs a path to a SCT file, 'C:\ProgramData\PpybhVgPWdvKplv.sct', and uses FOPEN to open it, indicating an intent to download and execute a second-stage payload. The presence of a hidden sheet further supports the malicious nature of the file.

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
58ee5b631e1e9d05ba133fa5aef31757d3f9dfd8710df54ac35d4c96a13b9e04		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1596807 bytes

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