Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 1d10d06227fbd0b2…

MALICIOUS

Office (OOXML) / .XLSX

1.03 MB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-04-27
MD5: a2aa392193ca1ac5d4c8dfb0cd8d0ac4 SHA-1: dc36b5aeb7bb8c2dc7b21a8a6e8eb65e7604a208 SHA-256: 1d10d06227fbd0b2f1254ff5f644f2a009fa27b7fdcc8392c32b5f198af48c49
180 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file contains Excel 4.0 macros, identified by the OOXML_XLM_MACROSHEET heuristic. These macros contain WinAPI strings like CreateDirectoryA and Kernel32, indicating they are designed to perform system-level operations. The script attempts to create directories and execute 'calc', suggesting it's a downloader for a second-stage payload. The ClamAV detection explicitly names this as Xls.Downloader.Emotet-OOXML_XL, strongly indicating the Emotet family.

Heuristics 3

  • 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

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
emf_00.emf
877e4543f89ce8edb4ba9c66218abfc871d4a1c4f42f3f21f1e998a11b32f267		 ooxml-emf OOXML EMF part: xl/media/image1.emf 6145428 bytes
xlm_sheet_00.bin
7b8101fc2a3a581cae3ed75e750022933ba4a1a2d03b29d213d39fc67d9624b5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 2280 bytes

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