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

Static analysis result for SHA-256 8f589d50f7e1feb0…

MALICIOUS

Office (OOXML) / .XLSX

68.9 KB
MD5: 27165df5bf4b00d679832ab08ce8059a SHA-1: 45d172dc1c76e8ca7d23539012070f8e566daca3 SHA-256: 8f589d50f7e1feb05b55a219ade75a19accb435fa595c33b6c68fc66ace2abaa
130 Risk Score

Malware Insights

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

The sample contains an Excel 4.0 macro sheet that utilizes dangerous formula APIs like FORMULA, which can be used to execute arbitrary code. The macro appears to be constructing a complex string that likely represents a command or URL. This functionality is indicative of a downloader or initial access mechanism. The malformed ZIP headers are a minor artifact and do not impede analysis.

Heuristics 4

  • Excel 4.0 macro sheet (1 sheet(s)) critical OOXML_XLM_MACROSHEET
    Malformed OOXML local headers contain an Excel 4.0 (XLM) macro sheet. XLM was a major Office malware vector during 2020-2022 and is rarely used in modern legitimate workbooks.
  • Dangerous XLM formula APIs: FORMULA, RETURN critical OOXML_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet uses formula APIs that call directly into Win32 (=CALL/=EXEC/=REGISTER/=FORMULA).
  • Malformed OOXML package with recoverable local headers low OOXML_MALFORMED_ZIP_LOCAL_HEADERS
    The OOXML ZIP central directory is invalid or missing, but local file headers expose a recoverable Office package. This can create parser divergence between tolerant Office/ZIP readers and scanners that rely only on the central directory.
  • 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_08.xml
d810cc87eb589e5f09a9a5cb06e9b818ff37e1b4d0032ba08fbf4b3620a5d223		 xlm-macrosheet Malformed OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3431 bytes

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