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

Static analysis result for SHA-256 6d598bc0fdbee480…

MALICIOUS

Office (OOXML) / .XLSX

202.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 4b6d8870670437a4116df43da8020ea0 SHA-1: c976a5198f50a119dca02f085c16851070593ac6 SHA-256: 6d598bc0fdbee4805f725edb60765130d4ad144821dcbe076064725f5490e0b5
310 Risk Score

Malware Insights

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

This Excel file contains critical Excel 4.0 macros that utilize dangerous API calls like FORMULA, EXEC, and REGISTER. These macros are designed to download and execute payloads, evidenced by strings like URLDownloadToFileA. The Workbook_Open macro also fires, indicating immediate execution upon opening. The presence of multiple IP addresses in the document body suggests these are potential C2 servers for the downloaded payload.

Heuristics 8

  • 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.
  • Dangerous XLM formula APIs: FORMULA, GOTO, HALT, EXEC, REGISTER 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
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_Open macro
  • VBA project inside OOXML medium OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 4 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 8

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
434cbac92f6a2c46f0bc4ae1ca7a3b0c578de25394cc02608cc3c0977523ed0c		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 21429 bytes
vbaProject_00.bin
421319bc0c842d04775cf1e696b30d221ec2baa08b0530e6be1058ae4d6a559d		 vba-project OOXML VBA project: xl/vbaProject.bin 24064 bytes
xlm_sheet_00.xml
e26278d9df62929caddc39c2675d1a93c805965a35896b4c4240468b728373e2		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 1190 bytes
xlm_sheet_01.xml
04a0524a3c786380e41e8b0640d0ac3993bd1a74ad2a1677e35f8a88369a9af7		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml 1174 bytes
xlm_sheet_02.xml
41c39894722730394a15e39c1e36f4d43b1d6ee757ad3a0bcf9949f7fa8e4183		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.xml 2866 bytes
xlm_sheet_03.xml
2b82c12e1298f5e52921c7e6e580246a70757d8584dc2921ac725339dc14a342		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet4.xml 2035 bytes
xlm_sheet_04.xml
9536b9d15d05d45ed9426d1a46c18a5661475241404d10bc9caf4e4a0dbaad4f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet5.xml 1611 bytes
xlm_sheet_05.xml
8bcd9bfd90b681f4e19e6e84eb9cc6e4d39af031cac9794160e21f5a5eef987d		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet6.xml 1426 bytes

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