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

Static analysis result for SHA-256 9818931574ed09e9…

MALICIOUS

Office (OOXML) / .XLSM

131.4 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 3ff89734f2c6a54fe79464e94151ce10 SHA-1: 4b4f24fec70071de89a76b70e12394a56efdcf62 SHA-256: 9818931574ed09e96ddc907c47907cfc6fbfad3f6bc3fca1c0f3b210c1d458f4
190 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

The sample is an XLSM file containing Excel 4.0 macros. Heuristics indicate the use of dangerous functions like FOPEN, FWRITE, and EXEC, which are commonly used to download and execute payloads. The ALERT function is used to display a deceptive message to the user. The reconstructed URL http://193.169.54.15/210.248.19 is likely used for payload delivery, and the reconstructed path C:\Program Files\Microsoft Office\Office16\XLSTART\excel.exe suggests an attempt to establish persistence.

Heuristics 5

  • 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, EXEC, RETURN 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.
  • 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
fa6a3052765c082c8cb7e01f9d6976b0dc991d33f157bfcab18a65dad9f8727f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 5541 bytes

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