Office (OOXML) / .XLSX malware analysis — malicious · 8af6e6ec8b4d613b

MALICIOUS

Office (OOXML) / .XLSX

146.1 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-04-06

MD5: 02456456ee0790ce555b503dc7865d86 SHA-1: 6f4b9910fa6fd310e666d2bd1c9bcbf5433a50f6 SHA-256: 8af6e6ec8b4d613b784142a302ad1e662230be7676ada1f4291b188eec3bb705

180 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The sample is identified as malicious by ClamAV with the signature Xls.Downloader.GreenOffice01220-9937699-0. Static analysis reveals the presence of multiple Excel 4.0 macro sheets within an XLSX file, indicating a downloader or droppper functionality. The macros are likely responsible for fetching and executing a secondary payload.

Heuristics 3

Excel 4.0 macro sheet (13 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: Xls.Downloader.GreenOffice01220-9937699-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.GreenOffice01220-9937699-0

Extracted artifacts 13

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `5cd0c206d1c0ea28c3457d4282c01ef21ffe4b14957e3e3ac64cfebf3d7de8dc`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	363 bytes
`xlm_sheet_01.bin` `58e234b9c9d686e8c506e684fef74670c2535741b5e96701437599bf84baf65d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.bin	1464 bytes
`xlm_sheet_02.bin` `fa336e04758c7bd5cad2da8d21bb8f5151827145d71e270b147e29611e497766`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	11832 bytes
`xlm_sheet_03.bin` `9394f61c80902255d30d3ad77b7529d71b7f5059409538e1568d5f76b746eee7`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet3.bin	82807 bytes
`xlm_sheet_04.bin` `9c6bdc3cf36bf03dd21b9f39c0a613d23b196aad0543052f150cb6732a531075`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet4.bin	17937 bytes
`xlm_sheet_05.bin` `8b7715d6b127c6c810bd615d8b9e96243c5d151d94f6a5bf4a2176c1b5d251d8`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet5.bin	37303 bytes
`xlm_sheet_06.bin` `c687cc03a7cddd68b7e16fdccac8a1cf5755614d3cc0f30368e5ca6dd1a50c61`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet6.bin	65714 bytes
`xlm_sheet_07.bin` `9351a7dcb547693bb072da0d5ed56b914dbe3136b1d56394996b14300bc9e66a`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet7.bin	80820 bytes
`xlm_sheet_08.bin` `8f1fb8f6a9d6da4075b35bc189944cc736c2cda6d1350dfe1796822f1f078d15`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet8.bin	306255 bytes
`xlm_sheet_09.bin` `918d790ea30b947f53c24ec6c93580866dfd1c88cb8d916cfa8524a5f5053d7d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	2807 bytes
`xlm_sheet_10.bin` `c567b560932ba7c631862cd9a5633c21d3dc9a89eb01c427c064f8d90064130e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	2275 bytes
`xlm_sheet_11.bin` `7d5bc712f983bb5eeb78a6f77be5eca2f46f336bb5ebc9442788dca7e9c8b091`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet9.bin	463 bytes
`xlm_sheet_12.bin` `520a06a1f576b348abae440ac838037a218552f2e3d2ee2a65c276ec62337831`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	5345 bytes

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