Malicious Office (OOXML) / .XLSM — malware analysis report

Static analysis result for SHA-256 3837ff7d2110e930…

MALICIOUS

Office (OOXML) / .XLSM

138.1 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: e0e2222230d999c75230b9b070116637 SHA-1: 70c1fa3bca50bea118f186175caf1e1717aa23e8 SHA-256: 3837ff7d2110e930ac8fcd7f72cf71009dc910674aa64f270044f8cf6d3805e5
250 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros, specifically using the dangerous functions FOPEN, FWRITE, and EXEC. The macro attempts to construct a path 'C:\ProgramData\z' which is likely where a downloaded payload would be written. The ClamAV detection as 'Xls.Downloader.Dridex122100-9913248-0' further supports its role as a downloader. The use of these functions indicates an intent to 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
46793e3b94cf0ef4805c3c8c6f66e572e1547d8dce951c34c29d0e549fec684d		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 5061 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.