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

Static analysis result for SHA-256 1f325ca84c44d050…

MALICIOUS

Office (OOXML) / .XLSM

216.2 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: fae13812d8feb6b29dc72430c638a728 SHA-1: 0c0833a962d410557d4fa31481d259b80d65e61d SHA-256: 1f325ca84c44d05053b8a29a083b40ba8533aa2490a12aac76030188aef8d028
250 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell

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\WMeCUbctrkB.sct'. The EXEC function is constructed using CHAR functions to build the command 'MSHTA C:\ProgramData\WMeCUbctrkB.sct', indicating the intent to download and execute a second-stage payload. The ClamAV detection as 'Xls.Downloader.DridexCyan08210-9887648-0' further supports its role as a downloader.

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
6b709ec86f8cb0e45b06416d8aba6562eb0a049b7b4adc3e0b2b9e7a1d3d985f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 186643 bytes

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