Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 40cf12531faff24f…

MALICIOUS

Office (OOXML) / .XLSX

240.1 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-06-14
MD5: f5429b499d0be8916ae4a1f9fe30e900 SHA-1: 001504229c39a6d629372503bc3e465688e235c6 SHA-256: 40cf12531faff24fc7f204ed2c846238a47981fe258f0ae9cf23116f52c99639
180 Risk Score

Malware Insights

Emotet · confidence 95%

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

The sample contains critical heuristic firings indicating Excel 4.0 macros and a reassembled payload. The macros directly reference multiple URLs, such as 'ordisois.com/9bVaa06WXzsj/Knhfn.png', which are likely used to download a second-stage payload. The ClamAV detection explicitly names this as 'Xls.Downloader.Emotet-OOXML_XL', strongly suggesting the Emotet family. The script also reconstructs paths like 'C:\Paetrio\Mnarost\Mnbense.OOOOCCCCXXX', indicating potential file drops.

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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