Dridex — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 3ef72317656dc01f…

MALICIOUS

Office (OOXML) / .XLSX

139.3 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 8fb7ef578a16512cd42086c9a209babb SHA-1: 4731652a07803e5993b0a31f8f5c5d2c884b714a SHA-256: 3ef72317656dc01ff09c2fe6ff823f8f6345bdb622693b1d166a7181ac1a2fd3
250 Risk Score

Malware Insights

Dridex · confidence 85%

MITRE ATT&CK
T1204.002 User Execution: Malicious File T1059.005 Command and Scripting Interpreter: Visual Basic for Applications T1027 Obfuscated Files or Information T1105 Ingress Tool Transfer

The sample is an XLSX file containing an Excel 4.0 macro sheet with an Auto_Open trigger. The macro uses dangerous XLM functions such as FOPEN and EXEC to drop and execute a payload. Specifically, it attempts to write to C:\ProgramData\RFyhDlMKW.rtf. The ClamAV detection specifically identifies this as Dridex.

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
8b215e275de7fbd75be14cca9b2d558993565a5e6bc058c6b4d2c64cfa36e802		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 4800 bytes

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