Office (OOXML) / .XLSX malware analysis — malicious · c5a3596beea95ed9

MALICIOUS

Office (OOXML) / .XLSX

268.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-02

MD5: c3ae9aa53987b4be5ef9ad6caef211f7 SHA-1: bfe929c33031444e9c9d03d9a059f448730e0d3d SHA-256: c5a3596beea95ed97e985602fe1763f2a8a036f0a6c3b2a24445e4a1008197bf

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Visual Basic

The file is identified as malicious due to the presence of multiple critical heuristic firings indicating Excel 4.0 macro sheets embedded within an XLSX file. The ClamAV detection name 'Multios.Malware.Agent-9967226-0' further confirms its malicious nature. The embedded XLM macro sheets, though heavily obfuscated and truncated in the provided excerpts, are characteristic of older Excel macro abuse for executing arbitrary commands or downloading further payloads. The primary attack pattern involves leveraging these macros for initial execution.

Heuristics 3

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.
ClamAV: Multios.Malware.Agent-9967226-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Multios.Malware.Agent-9967226-0

Extracted artifacts 10

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `1434b2bef33f9d8608b044437f48428e0298120e7017f631a2f33ba56aa6c752`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	322 bytes
`xlm_sheet_01.bin` `04a1c8c42066978968a402f8a04ce6a5a7673ecef4b9debc084649b52b747f64`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	2151 bytes
`xlm_sheet_02.bin` `765804c19d50bdd3bcc0391b1b9907ad74cc8149c930eb53ac36c0ed226f6de5`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	484 bytes
`xlm_sheet_03.bin` `39bea9fab1c795173046b51b75a53296ad66f29d76b487594d693a8390fbe92c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	484 bytes
`xlm_sheet_04.bin` `a6b98894165c30b3d44d75e60bb0a628e7ecada95b399f9412700fb2b0674464`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	428 bytes
`xlm_sheet_05.bin` `0d7e2c72dfab2ccd23720ac96f72180b9d1cef3452c51624561364c9943be252`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	484 bytes
`xlm_sheet_06.bin` `c06f64468ac5923dcab4a106464d68314b609b115aa2e65526acb7d8e698561f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	484 bytes
`xlm_sheet_07.bin` `e78a0903c52a61f894d5702c5711f1a752800c144bcfc4cc3d9ea865cf5194b2`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	428 bytes
`xlm_sheet_08.bin` `3f0408b1671e6462403801fc8b3914288e73bf7bc2458e5f2ed94327d170c160`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet7.bin	428 bytes
`xlm_sheet_09.bin` `84adc44516a7e45de092091efae98c83b606d8196e202b922a66afc0dabdceb0`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet8.bin	348 bytes

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