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

Static analysis result for SHA-256 b2afa6adb5e3cc06…

MALICIOUS

Office (OOXML) / .XLSM

84.2 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: d6e775dc43747d035bbf1797cc19a310 SHA-1: 1fc8e4dde2a87afa5c08fce1ef36bc65727b9f08 SHA-256: b2afa6adb5e3cc0673bcea1129c3701f96adb0be3b9b2585f90eead79ed8e156
180 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File T1105 Ingress Tool Transfer

The sample is an Excel 4.0 macro sheet that utilizes dangerous functions like CALL and EXEC. The document body contains obfuscated strings that resolve to multiple URLs, indicating an intent to download and execute a second-stage payload. The use of Excel 4.0 macros and the download mechanism are characteristic of macro-based malware delivery.

Heuristics 4

  • 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: CALL, EXEC, FORMULA.FILL, 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.
  • 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
6bb1fa7b25c4a31dd2d66243f24bc2b4809a5ecf6b1ca9480c724b6e46bd7687		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 238359 bytes

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