Emotet Office (OOXML) / .XLSX malware analysis — malicious · 9fce71a05d5b62be

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: 06b57b161bc1a188954cc53a46c78165 SHA-1: 724e393843fcb788466ba48ca9b563b85483937d SHA-256: 9fce71a05d5b62be31725d2f839bedc096d9aa9f485d815635df3583e2c593e5

180 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The file contains Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. These macros leverage WinAPI functions like CreateDirectoryA and execute external commands such as 'regsvr32' and 'calc'. The ClamAV detection explicitly names this as 'Xls.Downloader.Emotet-OOXML_XL', strongly suggesting the Emotet family. The macros appear to be designed to download and execute a second-stage payload, likely by creating directories and then using 'regsvr32' or 'calc' to launch malicious content.

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.

Filename	Kind	Source	Size
`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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