dridex — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 8aa75d5cf72e1fd0…

MALICIOUS

Office (OOXML) / .XLSX

136.5 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: ff88069068413d77f1cc92da5ad0abad SHA-1: 08902275c9dbe38d6b7e550c34eb57cda731530f SHA-256: 8aa75d5cf72e1fd0282c2b33e53d79b1fe84080aeebccbfd63ba947834af4cc3
250 Risk Score

Malware Insights

dridex · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer T1059.003 Windows Command Shell

The file is an Excel 4.0 macro-enabled spreadsheet. Critical heuristics indicate the use of dangerous XLM functions like FOPEN and EXEC, which are commonly used to download and execute malicious payloads. Specifically, the macro attempts to write to the file C:\ProgramData\oiwVrqxryIcO.rtf, likely to stage a second-stage payload. The ClamAV signature also points to 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
93443028f261959e6bd7da8cc0d779424bce9ad9e6745b1cf5164746b491debd		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 5072 bytes

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