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

Static analysis result for SHA-256 49558300c4315c8c…

MALICIOUS

Office (OOXML) / .XLSX

154.0 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300
MD5: 6a44858ca2fe28f5e2c4eed2c5a360e4 SHA-1: e793cbf64ad364c93e3a673a090977a3434cb6d9 SHA-256: 49558300c4315c8c53216a8c17e32ff87ca4be34547ab064de7d872d429bb3f3
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The sample is an XLSX file containing embedded Excel 4.0 macro sheets. These macros are known to be used for executing arbitrary commands, often to download and run further malicious payloads. The heuristics indicate the presence of these macro sheets, suggesting a command execution attack pattern. No specific IOCs were extracted from the macro content itself due to truncation.

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
9a232684b90b1697660b058dac0594697a629fc26ba9e0c572e4e8b3c6d09add
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 5899 bytes
xlm_sheet_01.bin
86d47db54f15ba79e074bf90a680ee1fab1f3289b1916ec55a3001da53ffb657
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin 1158 bytes
xlm_sheet_02.bin
6e9f760f0197fd4535c8f2ecca590c8bedd4b8505085915e283f4133345daa26
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin 6203 bytes