Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 78dc2ee864d4327d…

MALICIOUS

Office (OOXML) / .XLSX

240.1 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-05-06
MD5: 315e355a2d93a2a428c3c254603fd0bf SHA-1: e36411bf8bb922bd722acc18be4282712a56f3c1 SHA-256: 78dc2ee864d4327da4cc47c743dd09853cbe69ff63393126f97aee27dbf5c3a6
180 Risk Score

Malware Insights

Emotet · confidence 95%

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

The sample contains Excel 4.0 macros, identified by the OOXML_XLM_MACROSHEET heuristic. These macros are designed to reassemble a payload from CHAR() and split formulas, as indicated by OOXML_XLM_REASSEMBLED_PAYLOAD. The extracted URLs like 'ordisOS.com/9bVAa06WXzsj/Knhfn.png' suggest the macro's intent is to download and execute a second-stage payload. ClamAV detection confirms this as Emotet malware.

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.
  • XLM payload reassembled from CHAR()/split formulas critical OOXML_XLM_REASSEMBLED_PAYLOAD
    An Excel 4.0 macro sheet builds its payload inside the formula token stream by concatenating per-character CHAR() calls and string fragments, so no WinAPI name, shell command, or URL is ever contiguous in the .bin for a literal-bytes scan to find. Reassembling the formulas recovered download/execute API names, LOLBin commands (regsvr32/rundll32/mshta/wmic/powershell), or a payload URL — the de-obfuscated download-and-run kill chain.
  • 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
56ddade77d7e32930aed597b7717dc3eff76587b10e692229752e1522d34b56e		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 998 bytes
xlm_sheet_01.bin
6596a1a91ff1e8511c9bacd26b0ed25c9acae41209ca6bf1af5b0af2340b0150		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.bin 2652 bytes
xlm_sheet_02.bin
4aa675529670262d62d2072b2082c4d2e236f5f4a3a27db04178011a4f7c7c65		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.bin 1336 bytes

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