Office (OOXML) / .XLSX malware analysis — malicious · 411a4587bc2cde60

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: e43c122ad8c35adc9317dd8aa38d2c3a SHA-1: de2d955220aad0b52467426bb95301f4939aa724 SHA-256: 411a4587bc2cde60c95a72cdbbba4d283bd8ce4edc8b479c690ad2f10eea1269

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Visual Basic

The sample is an Excel file containing multiple Excel 4.0 macro sheets, as indicated by the OOXML_XLM_MACROSHEET and OOXML_XLSB_INTL_MACROSHEET_IN_XLSX heuristics. The ClamAV detection further confirms its malicious nature. The embedded macro sheets appear to be obfuscated, but the presence of multiple macro sheets strongly suggests an attempt to execute arbitrary code. The primary attack pattern is likely the execution of these macros to download and run a secondary payload.

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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