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

Static analysis result for SHA-256 f4366a50e2a86f65…

MALICIOUS

Office (OOXML) / .XLSM

249.8 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 727ddadcfb432b1c5336338ffb56b451 SHA-1: 501a2bc865a4d41de9485fb2035c2d3e827082e1 SHA-256: f4366a50e2a86f65bccda978326b0ed301ad12bdb8e37ef928ddb992467d8a19
190 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros. The macros utilize dangerous functions like FOPEN, FWRITE, and EXEC to write and execute a script file. The script file path is constructed by concatenating character codes, resulting in 'C:\ProgramData\LqtQhyDEkFy.sct'. This indicates the macro's intent is to download and execute a second-stage payload from a local path, likely to evade network-based detection.

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
9aff9e6b94e9445ad3ebcee6687bed3352a3d9e33b345f8e3a0e17051a971597		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 700518 bytes

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