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

Static analysis result for SHA-256 ad1466bffb69c97d…

MALICIOUS

Office (OOXML) / .XLSM

93.4 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300
MD5: b9983a83761a6ad6e0750e2fb297e581 SHA-1: 4d5253d2501f947aaf12dd922ca958d2cc09a274 SHA-256: ad1466bffb69c97dba06d5106929c4ab251955462480f7901c21fb4709447e31
200 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1218.010 System Binary Proxy Execution: Regsvr32 T1059.001 Command and Scripting Interpreter: PowerShell

The file is an XLSM document containing Excel 4.0 macros. Heuristics indicate the use of dangerous XLM functions like CALL and EXEC, which are often used to download and execute payloads. The document body contains obfuscated strings that appear to be URLs and the command 'regsvr32.exe', suggesting the execution of a second-stage payload. The macros likely download and execute a payload from one of the embedded URLs.

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: EXEC, CALL, HALT, FORMULA.FILL 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.
  • Suspicious extracted artifact medium EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • 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
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac
    • http://schemas.microsoft.com/office/spreadsheetml/2014/revision
    • http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
dbd5b4cab5273f47d1adf390a0d03ac210ef33cf9bc8ef6f5a64ee3c8df213d9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 213379 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 2 shell/COM execution token(s).

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