Dridex — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 db75339365f8d750…

MALICIOUS

Office (OOXML) / .XLSX

150.0 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 38e2ab715040bb7bcbe0db67f2afcb29 SHA-1: 13162e9cdb8fa994cfb71af8818d570ba89d9318 SHA-256: db75339365f8d7508bc581d5e469b0a18d9ba166265230e537eb9291f78c7c69
250 Risk Score

Malware Insights

Dridex · confidence 90%

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1059.001 PowerShell T1204.002 Malicious File T1105 Ingress Tool Transfer

The file is identified as a malicious Excel 4.0 downloader by ClamAV. The embedded Excel 4.0 macros utilize dangerous functions like FOPEN, FWRITE, and EXEC, indicating an intent to download and execute a second-stage payload. Specifically, the macro attempts to write to 'C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup\svchost.exe', suggesting an attempt at persistence. The macro also constructs a string that appears to be a URL for downloading the payload.

Heuristics 6

  • 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.
  • 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: FOPEN, FWRITE, EXEC, RETURN 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.Dridex122100-9913248-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Dridex122100-9913248-0
  • 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
083f267f57e0f7e7eac2b6ea9ca6b0f2c616c6c530d861039659448ddecf6a30		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 5880 bytes

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