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

Static analysis result for SHA-256 22af401346ef1fcd…

MALICIOUS

Office (OOXML) / .XLSM

210.4 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: f2f33efa9846db6f43a9dd085782e01b SHA-1: c3371f1ab559e0cf9892e624ef5eee2827f9a6ad SHA-256: 22af401346ef1fcdc1d75b14c560c91d6032d75b8ffc56e4ab23aeb4e1429313
250 Risk Score

Malware Insights

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

The file is an XLSM document containing Excel 4.0 macros. The macros utilize dangerous functions like EXEC and HALT to execute a script located at 'C:\ProgramData\oCbYgfmWLTgiXE.sct'. This indicates a downloader or dropper functionality, aiming to execute a secondary payload. The ClamAV detection as 'Xls.Downloader.DridexCyan08210-9887648-0' further supports this. The specific script path and the EXEC function call are the highest priority IOCs.

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: EXEC, HALT, FOPEN, FWRITE, FCLOSE 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.DridexCyan08210-9887648-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.DridexCyan08210-9887648-0
  • 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
f728e240fee95cb260d978bec75996b4e7510b670542fad50ca981dd773f35d7		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 124572 bytes

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