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

Static analysis result for SHA-256 111de7cc589d7013…

MALICIOUS

Office (OOXML) / .XLSX

197.7 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: f4853f40a2bd21ec22350a63a6419b2c SHA-1: 84d04a871d10dffab40847ccc19ce500e078224d SHA-256: 111de7cc589d7013a7f2d20f782dfbff2b90c141d69ce66fb106f63b8bc17beb
310 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution T1105 Ingress Tool Transfer

This Excel file contains multiple Excel 4.0 macro sheets that utilize dangerous functions like FORMULA, GOTO, and HALT. The macros are designed to call Win32 APIs such as URLDownloadToFileA to download a file and then execute it using rundll32. The reconstructed command for execution is 'rundll32 ..\lertio.cersw1,DllRegisterServer' and similar variants, indicating a downloader functionality.

Heuristics 7

  • Excel 4.0 macro sheet (6 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: FORMULA, GOTO, 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.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
  • ClamAV: Xls.Downloader.GreenEnable052-9863734-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.GreenEnable052-9863734-1
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 6 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://ns.adobe.com/xap/1.0/
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#
    • 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 6

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
e26278d9df62929caddc39c2675d1a93c805965a35896b4c4240468b728373e2		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 1190 bytes
xlm_sheet_01.xml
b7f12cc848c0344b1a5988c23e28d66931cabf93578aa111050b66b24515bc26		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml 3173 bytes
xlm_sheet_02.xml
885dac7b9ca2b9e8230baf49dad2ec27d3477b45eb4960d36b69b3166c4addb8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.xml 2299 bytes
xlm_sheet_03.xml
14198d56b3e501819788d2ba3deb676eae1c92f5b98789f221df62060b8b227d		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet4.xml 1481 bytes
xlm_sheet_04.xml
37cb7aa1e44520111e622e68f961c06b193624824122bd99088e7c0d058baf3c		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet5.xml 1469 bytes
xlm_sheet_05.xml
68e2eada477a01dd45889d7781ac27297df589224a5824d7ff63a37df7f5bc75		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1476 bytes

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