Trickbot — Office (OOXML) malware analysis

Static analysis result for SHA-256 4d55f412d602866b…

MALICIOUS

Office (OOXML)

119.0 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300
MD5: 55712f4294327fcacc8759b48871d4fa SHA-1: 63aa04755a401d68905eccf2c91b798d20a63de5 SHA-256: 4d55f412d602866b1c9d5fa915a0439aaec265a166bdc49a767708013316a37c
250 Risk Score

Malware Insights

Trickbot · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution T1105 Ingress Tool Transfer

The file is an Excel workbook containing multiple Excel 4.0 macro sheets, identified by critical heuristics. These macros utilize dangerous functions like FORMULA and CALL to execute external commands. Specifically, the macros attempt to download a DLL named 'zvbxnx.dll' from 'http://162.248.225.95/d.php' using URLMon and then execute it via 'regsvr32 -silent ..\zvbxnx.dll'. This behavior is consistent with a downloader for malware like Trickbot.

Heuristics 6

  • Excel 4.0 macro sheet (5 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, HALT 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.Trickbot07210-9880007-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Trickbot07210-9880007-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 1 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 5

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
ead8cdcc18ca09a9f1328ae9399750e4baa9e7c6fb8ca17b0bd770971aea3f01		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 229062 bytes
xlm_sheet_01.xml
3a34f0c119b58147309018ddbc9805599240f8e8e91c55e24eb1ebd1c199c1e2		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml 1689 bytes
xlm_sheet_02.xml
b062a709274dd5fc840799089ddb6864ced137e2315ba08b0299f6065a16b375		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.xml 1773 bytes
xlm_sheet_03.xml
57537cc8466ada117081e749fe7167446f3f5d029fd4fb1612ea0261027bc6c1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet4.xml 1778 bytes
xlm_sheet_04.xml
9cf98f4732ae983fd46d8cf179488facaeec3ec6d78e683880682236b3dbdb0e		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet5.xml 1879 bytes

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