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

Static analysis result for SHA-256 dddb5591ca031d06…

MALICIOUS

Office (OOXML) / .XLSM

251.8 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: cfee648208634c4fe5201d3574bc7e5a SHA-1: 44ce889559c8bea258994fbfab5f9192182f103a SHA-256: dddb5591ca031d06cf0778ba22594d46a4ab09f285027fe55e01297838e714de
190 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1059.003 Windows Command Shell

The sample is an XLSM file containing Excel 4.0 macros. These macros utilize dangerous functions like FOPEN, FWRITE, FCLOSE, and EXEC to write a script to disk and then execute it. The script is constructed from character codes and appears to be a SCT file, likely a Windows Script Component. The macro code reconstructs the path 'C:\ProgramData\tXwKktPwAWWuXaY.sct' and uses the EXEC function to run it, indicating a downloader or initial execution stage.

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
5847b2be935751e172b7ca5b5c2f5088191535dc7e6369fc9ea4d916a6fb71e5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 714507 bytes

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