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

Static analysis result for SHA-256 1feeacd85d4c7dfe…

MALICIOUS

Office (OOXML) / .XLSM

273.0 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: 315ac4cb1626d45a3988271d68f50974 SHA-1: a80338304fa25d68366de8970d5b0c88be3d0f3d SHA-256: 1feeacd85d4c7dfebe07a2851d604eab37dcd9a09869f7e7686f36fc38ca29d9
190 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros. The macros utilize dangerous functions like FOPEN, FWRITE, FCLOSE, EXEC, and CALL to write and execute a script file located at C:\ProgramData\slGEMZalIsQxj.sct. This indicates a downloader or dropper functionality, aiming to execute a second-stage payload. The use of these specific XLM functions is a strong indicator of malicious intent.

Heuristics 5

  • 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, FCLOSE, EXEC, HALT 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.
  • 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
5d9045664e3bdc6286d55673b9e02157c8d0381757c683102cc6ee1ea6785a17		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 889986 bytes

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