Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 31c4e6a73b09b6db…

MALICIOUS

Office (OOXML) / .XLSX

143.8 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 9275458d705a6fd11fb587d24c2c3eab SHA-1: 38b1ccc1432821a013ca0bb74efc1fdf5828de74 SHA-256: 31c4e6a73b09b6db98a3c10c13f96db8bae519e4349fea3e383688b5f79476ac
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Service Execution T1059.001 PowerShell: PowerShell T1204.002 Malicious File: Malicious File T1105 Ingress Tool Transfer

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by multiple critical heuristic firings including OOXML_XLM_MACROSHEET and OOXML_XLM_DANGEROUS_FN. The macros utilize dangerous functions like FORMULA to call Win32 APIs, which are used to download and execute payloads. The reconstructed URL 'http://wyldfyrearabians.com/cgi/1HyEagziS/' is used in conjunction with rundll32.exe and a local file path '\Windows\SysWow64\..\lnu.ocx' to likely download and execute a second-stage payload. The ClamAV detection name 'Xls.Downloader.EmotetRed022215-9938912-0' strongly suggests the Emotet family.

Heuristics 6

  • Excel 4.0 macro sheet (7 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.
  • Excel 4.0 Auto_Open defined name critical OOXML_XLM_AUTOOPEN_DEFINEDNAME
    Workbook defines _xlnm.Auto_Open or _xlnm.Auto_Close while containing an XLM macro sheet. This is the OOXML/XLSB auto-execution shape for Excel 4.0 macros.
  • Dangerous XLM formula APIs: FORMULA critical OOXML_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet uses formula APIs that call directly into Win32 (=CALL/=EXEC/=REGISTER/=FORMULA). These are the primitives used to download payloads, write files, and start processes from an XLM macro without invoking VBA.
  • ClamAV: Xls.Downloader.EmotetRed022215-9938912-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetRed022215-9938912-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 9 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://schemas.openxmlformats.org/spreadsheetml/2006/main
    • http://schemas.microsoft.com/office/excel/2006/main
    • http://schemas.openxmlformats.org/officeDocument/2006/relationships
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac
    • http://schemas.microsoft.com/office/spreadsheetml/2014/revision
    • http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 7

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
845190ff95687dd3bed60f8155a4703d187c9ac3d57c95b5f1e5fbccfcda8bf1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3818 bytes
xlm_sheet_01.xml
eb8dc692c1dd2153c89791e81ba8dde6872cd513333852aece5cf5246e9e9be7		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1339 bytes
xlm_sheet_02.xml
a2c24226987a123df54bf20bea623cddda5aa0848671b3a68fae646b034b0c13		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1334 bytes
xlm_sheet_03.xml
1afc49d1079b956e7cd6c79b3050d7c6146176d5f88b0641a059978149dc558f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.xml 1337 bytes
xlm_sheet_04.xml
f2beecaf3836e6877dc1d8dcccc0ec6a61ee971bb99fad7ea199d9c4485833ad		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet4.xml 1341 bytes
xlm_sheet_05.xml
33833c2bb127cd3da704c0fa39beca9ede4ef247ba80706d40a7c8cb5fdddbee		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet5.xml 1256 bytes
xlm_sheet_06.xml
9600e9bf835b635afc1c3dbd6b85e16bd1c645dbab403a3c6d8610cff36b8262		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet6.xml 1177 bytes

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