Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 9fd646098e76d065…

MALICIOUS

Office (OOXML) / .XLSX

1.20 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-04-28
MD5: 7e75586412a690fd3c015847867940de SHA-1: 83928ea70fcd2a95c4ffb03febec564b19ac1876 SHA-256: 9fd646098e76d065b972a8ebf5aa47ab3c5df2b9064048332a23d84fa3fd704c
200 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The critical heuristic 'OOXML_XLM_BINARY_WINAPI_STRINGS' indicates the presence of Excel 4.0 macros that utilize WinAPI functions. The extracted script content shows calls to 'CreateDirectoryA' and references to filenames like 'C:\Jugfstati\Nydyzc.occcxx', suggesting the macro's intent is to create directories and likely download and execute further stages of the malware. The ClamAV detection explicitly names this as 'Xls.Downloader.Emotet-OOXML_XL'.

Heuristics 4

  • Excel 4.0 macro sheet (1 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.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
  • 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
  • Embedded OLE object medium OOXML_OLE_OBJECT
    Document contains an embedded OLE object

Extracted artifacts 4

Files carved from inside the sample during analysis.

FilenameKindSourceSize
ooxml_oleobject_00.bin
4bad71bbe5a530a4ecb623fd5daea8cac187a6dc6f61565c470ee7261327c19f		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/oleObject3.bin 2706944 bytes
ooxml_oleobject_00_ole10native_00.bin
908a9061823bfb3e7f9f6928ed4da796b96e6132468adee38685b01e1078a8c7		 ole-package OOXML xl/embeddings/oleObject3.bin Ole10Native stream: Ole10Native 2683300 bytes
emf_00.emf
33c042ac8babe18b25e94413a9c9fb98a54bbce22a09d1e6fd07f6be12b2b5ec		 ooxml-emf OOXML EMF part: xl/media/image1.emf 5367000 bytes
xlm_sheet_00.bin
87833ac5dd31547f952341facc430f1957f03f6a8fc0ad92753af33aeaac7613		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2427 bytes

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