Office (OOXML) / .XLSX malware analysis — malicious · 4e9310b547aaef12

MALICIOUS

Office (OOXML) / .XLSX

96.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300

MD5: b909c157cac4a60d6eb1cc614deb4de5 SHA-1: 7d7d793c365724e3882a320c8ec366b27929fe0b SHA-256: 4e9310b547aaef12d30c9f4af474a168d5bafdcf3b5379a914c5840e76d28bac

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. These macros are designed to execute arbitrary code, which is a common technique for initial payload delivery. No specific family could be identified due to the generic nature of the macro execution.

Heuristics 2

Excel 4.0 macro sheet (7 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 7

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `c37fba766abd6d156918a643e026b438f9eb0eaa225c144756cd2a5c6fda4519`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	484 bytes
`xlm_sheet_01.bin` `22bba77ccfeebe8e5c4e883612c26774cb0b357b34f9b8f821432aab3ada7cb3`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	484 bytes
`xlm_sheet_02.bin` `a54cfa9ba41e5598d383926a84d25941debd28f24c9934cba5a5f56d9097ca69`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2076 bytes
`xlm_sheet_03.bin` `cc1fea1c5ed0ee9ba6377487e147436c2cdc066a48105c36d0aca3c1995417f4`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	484 bytes
`xlm_sheet_04.bin` `fc16eb2a62981f93b25a935d0a0fb49d33f90429021cb43f6e7f301424f17a92`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	484 bytes
`xlm_sheet_05.bin` `e1559372370dc0c7c16b816f71c2d5acc0e30cc8878cffe531ed647dae733bb2`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	484 bytes
`xlm_sheet_06.bin` `1f384d37a830103e6e157bda73c1f5bba7a0a8db52a6ba5a8d8560d3886df131`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	484 bytes

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