Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 f0fb73ecf629da18…

MALICIOUS

Office (OOXML) / .XLSX

238.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-15
MD5: 83f7e991cbbdd84be8136967589b087d SHA-1: 701bda1964c098385fa37f5c7c5e1b0486bfaa8e SHA-256: f0fb73ecf629da1883bcc6b508ac4bf2ea60885e1df8f6b2ab59b48ca1e5ddd1
180 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The file is identified as malicious by ClamAV with the signature Xls.Downloader.Emotet-OOXML_XL-af43432fbcb8603c-9980048-0, indicating it belongs to the Emotet family. Static analysis revealed the presence of Excel 4.0 macro sheets within the XLSX file. These macros are commonly used to download and execute secondary payloads, a hallmark of Emotet's delivery mechanism.

Heuristics 3

  • Excel 4.0 macro sheet (3 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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
2eee5ae961fe5d65f35cf8570602a23d6ff455536901fc8d2a2296dc48ce0fed		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.bin 2127 bytes
xlm_sheet_01.bin
76bb729a3fef1962dba3c4d4608bc67767a415d3068cfaefbab6dc04307f5716		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 428 bytes
xlm_sheet_02.bin
e107436a5f0bb0a25f454c2c3756c9b0d1befa58088a66751c1bc69dc47f10ec		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 428 bytes

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