dridex — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 cf0d6ea61f8e56f8…

MALICIOUS

Office (OOXML) / .XLSX

149.5 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 531039a455e1f0598cd201b785a1152a SHA-1: 4880df9e94090243029e54a34e941c70298401c7 SHA-256: cf0d6ea61f8e56f80f24792e356adeab2f92b6db2f980a9e5932415484f5b732
250 Risk Score

Malware Insights

dridex · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1204.002 Malicious File: User Execution: Malicious File T1059.001 Command and Scripting Interpreter: PowerShell T1059.003 Command and Scripting Interpreter: Windows Command Shell

The sample is identified as a malicious Excel 4.0 macro-enabled document. Critical heuristics indicate the use of dangerous XLM formula APIs such as FOPEN, FWRITE, and EXEC, which are commonly used to download and execute payloads. The ClamAV detection explicitly names this as 'Xls.Downloader.Dridex122100-9913248-0', strongly suggesting a Dridex variant. The embedded script uses these dangerous functions to likely download and execute a second-stage 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
b6343109e9f0eca9006c7018aaf434f0a1847705cdca45d899eb8be3dc3aa88c		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 4910 bytes

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