Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 36b1d9d678c80e1c…

MALICIOUS

Office (OOXML)

106.2 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 3082507a31c736cc39063b6e16eb8a9a SHA-1: 6099ab0b616c1619327cb0102384fcf64191997c SHA-256: 36b1d9d678c80e1cf5bd59f0fa11ab4c0f19a01cb0adc376d66a6dac6955aaf5
130 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

This Excel file contains two Excel 4.0 macro sheets that utilize dangerous functions like REGISTER, GOTO, EXEC, and HALT. The macros are designed to download a payload from the URLs http://45.84.1.195/ or http://185.82.219.131/ and execute it using 'rundll32 ..\Niolas.dll,DllRegisterServer'. The presence of hidden sheets and the use of these functions strongly indicate a malicious downloader.

Heuristics 4

  • Excel 4.0 macro sheet (2 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.
  • Dangerous XLM formula APIs: REGISTER, GOTO, 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 3 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://45.84.1.195/
    • http://185.82.219.131/
    • 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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
195a22194deb18d457e7a276044a8954c5a468f56b51b6a1ff34e52b2b6585ae		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 2129 bytes
xlm_sheet_01.xml
790f162dfe4d36146f6098416bb54d0d0a33d67d88c8fea35d57cce261bdd8f0		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.xml 1943 bytes

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