Office (OOXML) / .XLSX malware analysis — malicious · 59cd9dc7a9c2bc5f

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: fd9c34bf68cd57fe9bf33b3d837b43f8 SHA-1: 6aeb21d0067a98b0836d0ba16db95c0a624f8917 SHA-256: 59cd9dc7a9c2bc5f4d00c69e28c55d6622f8792fe87b016549c30e76736e3b58

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an XLSX document containing multiple Excel 4.0 macro sheets, indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. While the macro content is heavily obfuscated and truncated, the presence of these macro sheets strongly suggests an attempt to execute arbitrary commands upon opening. The specific commands and their targets could not be reliably determined due to the obfuscation and truncation of the script content.

Heuristics 2

Excel 4.0 macro sheet (10 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 10

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `bee3fd9d1ce99b02b35f5662e4de7e62bdd41e05deca34e537b522a1aeca442e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	322 bytes
`xlm_sheet_01.bin` `437e9f5e46f50f6264f1468611cb3a7016fd693f55a8d679ff97bada55b19d48`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2093 bytes
`xlm_sheet_02.bin` `bf9296aaf0e5b84a19f6b3ff4b9afe95753013f257b1d1c75c70cc1b08b9ad68`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	477 bytes
`xlm_sheet_03.bin` `a500f1ae4d898900a3144ae215bd4e3f47736c4875919f139ec5546ed6597e8b`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	428 bytes
`xlm_sheet_04.bin` `ab3f84691f75f808a265fd47fd2de553fe8c7cf42364c345d2da1035041ddb59`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	428 bytes
`xlm_sheet_05.bin` `333e01ee17df88556ba83b070e2d77a0478ddb01a29baf7fdef93732ee59798f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	428 bytes
`xlm_sheet_06.bin` `136f099ac6cb64e1d7601355d317ccd460b2865c1d11e5b443b06a6d14ea4197`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	428 bytes
`xlm_sheet_07.bin` `dbe22dd404c1f321e5a0fb3f96913e4db489106ba51a7dad6ad1e5cc3a952f21`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet7.bin	428 bytes
`xlm_sheet_08.bin` `cee664e2fc6f8587326643d7a2f63389c2e546edb39c94eedb830f20a7051f28`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet8.bin	428 bytes
`xlm_sheet_09.bin` `415f1451b36102d686540ecdf4d3c07a4666c68b1840c08ab5d0bff7af909409`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet9.bin	348 bytes

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