Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 b525557732a28973…

MALICIOUS

Office (OOXML) / .XLSX

206.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: b33909bab350fc3f680556b5ea714e18 SHA-1: d9945a4759f58df53872eea0e043b5482904f83e SHA-256: b525557732a28973a313e95a9152bf32e9b2ccbe873bcb6b3cebd9e9765cf04b
180 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic

The file is identified as malicious by ClamAV with the signature Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0, indicating it is an Emotet downloader. The presence of multiple Excel 4.0 macro sheets within an XLSX file strongly suggests macro-based execution. While the specific macro code is heavily obfuscated and truncated, the heuristic firings confirm the use of these macro sheets, which are commonly used by Emotet to download and execute further stages.

Heuristics 3

  • Excel 4.0 macro sheet (7 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 7

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
7c63eee8c970bef6e063050717340ff98d82c7a8c8ce77b33dd8b481bf64af39		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.bin 428 bytes
xlm_sheet_01.bin
067cceb164d2b4098c62a3c39eb4a992745017847d51f01ac3e90bed21337a70		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet6.bin 428 bytes
xlm_sheet_02.bin
b0468924ead80a1916bdf5316ed0b981bcdb82c9d750298d362d009099bcdfa9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet4.bin 428 bytes
xlm_sheet_03.bin
65e5518a72d4eaad2ca4c7df27f100258abbdfc238f6250080a7139e57dc6d82		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 2040 bytes
xlm_sheet_04.bin
7245190722d30d6407821c8323dc11af2c8682a68abe129e13a5647185ecaa2a		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 428 bytes
xlm_sheet_05.bin
de9abad22dc1b312843be997c75987cf18086048c080720cd7f94da44911a5a3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet5.bin 428 bytes
xlm_sheet_06.bin
d04ce6b725ca50924058f297a2ad325cc7974396cb7552036d145d5daa3b9dbb		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 428 bytes

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