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

Static analysis result for SHA-256 29f4fa56df55b1b5…

MALICIOUS

Office (OOXML) / .XLSM

86.2 KB Created: 2020-05-27 22:50:01 UTC Authoring application: Microsoft Excel 14.0300
MD5: a758f5bfaeb275b5dfaf5be55a8b087b SHA-1: eff178dfef00ee753f4a540107632e43ec4a4ef9 SHA-256: 29f4fa56df55b1b53b2a8a6b27d2816436a75153eaf0533cf7d788d7026d8366
108 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The sample is an XLSM file containing Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous functions like RUN and CALL to download a payload from the URL https://aonagenarian.eu/3/skp.dll. The script also appears to execute downloaded files using rundll32.exe or regsvr32.exe, indicating a downloader or droppper functionality.

Heuristics 4

  • Dangerous XLM formula APIs: RUN, CALL, HALT, FORMULA 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.
  • Excel 4.0 macro sheet (1 sheet(s)) high 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.
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 5 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 https://aonagenarian.eu/3/skp.dll

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
73a1add16933a11bc64355fc04de0049ef0df8f025e035ad76cc5725ac9a4fc6		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 70659 bytes

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