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

Static analysis result for SHA-256 18abe6592b401da7…

MALICIOUS

Office (OOXML) / .XLSM

253.9 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 7603bbe8f90b3ba203bfd28cef1af0d1 SHA-1: fcf860917b99c051aaafe6c795bf5928c3daa0ba SHA-256: 18abe6592b401da7fa93083af881c000bd491b989d646de3c610a3824c3319fe
190 Risk Score

Malware Insights

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

The file is an XLSM document containing Excel 4.0 macros. These macros utilize dangerous functions like EXEC and FOPEN to write and execute a script file named 'C:\ProgramData\XfIZuFwx.sct'. The use of these functions indicates an attempt to download and run a second-stage payload, likely for further malicious activity.

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
811eeefe8634fedf4ed4850ba07252fade1dcaad24a4b8c8af7f51572b5a307e		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 765526 bytes

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