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

Static analysis result for SHA-256 ac209fab68bf2562…

MALICIOUS

Office (OOXML) / .XLSX

155.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 5eb937c5e76f8b268d5986be44ab2b02 SHA-1: ab58004a151382225d8e63acf3b0af2d4fa1ba8a SHA-256: ac209fab68bf2562237efedb28cd06a792d30d3dc84fed804a9c8b667ac5d351
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The sample is an XLSX file containing multiple Excel 4.0 macro sheets, indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. These macro sheets are known to be used for executing arbitrary commands. While the specific commands are truncated in the provided evidence, the presence of these macro sheets strongly suggests an attack pattern focused on initial payload execution. No specific family could be identified.

Heuristics 2

  • Excel 4.0 macro sheet (3 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. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.
  • XLSB international XLM macro sheet hidden in .xlsx critical OOXML_XLSB_INTL_MACROSHEET_IN_XLSX
    OOXML package is named .xlsx but contains XLSB workbook parts and an international Excel 4.0 macro sheet. This hides XLM macro execution from scanners that trust the extension or only inspect XML worksheet parts. The technique is macro execution, not a document-parser CVE.

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
071ab5d76ce9ab21f90817d76a426d972884e27bd69cb6ce1815321698b736ce
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 3879 bytes
xlm_sheet_01.bin
f812aed1cdb78fbb53256a600c2c0a9d188330545dcadc46c11cb03b4047d883
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 6541 bytes
xlm_sheet_02.bin
8ec4a2aad501810799024d7fd8c159312f87c39a139b186e0f489583af847eb9
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 1314 bytes