Emotet Office (OOXML) / .XLSX malware analysis — malicious · 3a3fe1a5a53777ed

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 272f8079dbc02016e93a556f1b1e2fc8 SHA-1: bc55eec1d31329ca842d9ee6a5de2e9555b8c073 SHA-256: 3a3fe1a5a53777edc0bcb8503ab67ca5faeda2fb3de126be00256b5f84e6e306

180 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The sample is identified as an Excel 4.0 macro-enabled XLSX file, which is a common delivery mechanism for Emotet. The presence of multiple XLM macro sheets indicates the file is designed to execute embedded macros. The ClamAV detection explicitly names Emotet and flags it as a downloader. The macros themselves are heavily obfuscated but their structure and the heuristic firings strongly suggest they are responsible for downloading and executing 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: Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0

Extracted artifacts 10

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `a600c06266bbd0dd2b61dfcd96dbddd020e5f170c3c38b6dcb6601e0a598335b`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	322 bytes
`xlm_sheet_01.bin` `68be8c00857b18185ff0efb8ce0fc7dee973358028087aac0391f0de04fd7463`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin	2194 bytes
`xlm_sheet_02.bin` `831006bd0c553b0a91e53049f365208dac45a8febf71d9228e851897dfadc0a7`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.bin	477 bytes
`xlm_sheet_03.bin` `c21656b2108164807026268f3c90e971984d43f78f4ad8d0629615e7c816fd1b`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.bin	428 bytes
`xlm_sheet_04.bin` `4c84712dfb6cbb1c894d2e20e88ae297988dcebbb5983e8d204a6eb35559433d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.bin	428 bytes
`xlm_sheet_05.bin` `e98ba1032156b96d449962420d43c5579d2546bcffa300550b5879a220ba52cf`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.bin	428 bytes
`xlm_sheet_06.bin` `9d333dba9a33ad9b51bb0f6d0a215f0d5b3a70c36bd3f94c58bf82af3f604595`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.bin	428 bytes
`xlm_sheet_07.bin` `897e1d866cde58047a18fa0a80b9cfd322c031317c3ed7767f4a8fa4facff84c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet7.bin	428 bytes
`xlm_sheet_08.bin` `27d5fabe81e784fe70f5c731c1f56cde57615c49df63f803f4d10f289dc491e8`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet8.bin	428 bytes
`xlm_sheet_09.bin` `afdc61e17960ec6f9ed7ed69d731a47414b0ad9e84008649fb89ebf19cc5bca0`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet9.bin	348 bytes

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