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

Static analysis result for SHA-256 0b421b87c36302cb…

MALICIOUS

Office (OOXML) / .XLSM

320.4 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 271b9aa2476aca33609c50c52ae89af2 SHA-1: c16c72b53a97fd5685e27ecb0a7adb5f64f8c9a2 SHA-256: 0b421b87c36302cbad0135de0e6e6f4ff8968e3d2d4ea9d5bda1462d8ef14e49
190 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros, including an Auto_Open defined name, which is a strong indicator of malicious intent. The macros utilize dangerous functions like EXEC and FOPEN to write and execute a script located at "C:\ProgramData\bFWERerWbW.sct". This indicates the file's primary purpose is to download and execute a secondary payload, likely for further system compromise.

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
132dac6715dc813128eeb6459479d2b7455e047e1389e88f7b95687028636beb		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1594216 bytes

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