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

Static analysis result for SHA-256 56c2a6cd514956d8…

MALICIOUS

Office (OOXML) / .XLSM

252.6 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: fd7075efa74442ec550ba1b0613f0db3 SHA-1: cc34b9d08b301523a1ee0f1cce90fd3a9f9c4c6b SHA-256: 56c2a6cd514956d83ac3d9f810ca1d942ba929f29a9af1d37aee3a1ce54a0283
190 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File Execution: Malicious File T1059.005 Command and Scripting Interpreter: Visual Basic T1105 Ingress Tool Transfer

The sample is an XLSM file containing Excel 4.0 macros. Critical heuristics indicate the use of dangerous functions like FOPEN, FWRITE, FCLOSE, and EXEC, which are used to download and execute payloads. The macros construct a path to a script file, 'C:\ProgramData\OyIGHoID.sct', and then use the EXEC function to run it. This indicates the file's purpose is to download and execute a second-stage payload.

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, 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.
  • 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
88b35f541874704229535b056044a7664d05359f5ec1940c72b47fc9e9b961fd		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 717721 bytes

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