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

Static analysis result for SHA-256 8df7d1c0c37a5199…

MALICIOUS

Office (OOXML) / .XLSM

185.5 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 8b631bad0869713bdfb6ba803d971283 SHA-1: 74e21a99c75d20c0bd76db5d1a77c39b1721dfc7 SHA-256: 8df7d1c0c37a519963e31bd2c7fd34b1cb5de232ee3bd9b1ab89878054d08715
242 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

The sample is an XLSM file containing Excel 4.0 macros, which are known to be used for malware delivery. The heuristics indicate the use of dangerous XLM formula APIs like FORMULA.FILL, which can be used to download and execute payloads. The ClamAV detection as 'Xls.Downloader.IcedID' further supports this. The script's intent is to download and execute a second-stage payload, as indicated by the use of FORMULA.FILL and the downloader family name.

Heuristics 5

  • Excel 4.0 macro sheet (3 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.FILL 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.
  • ClamAV: Xls.Downloader.IcedID-9f1f1d193a2a2a2b-9951463-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.IcedID-9f1f1d193a2a2a2b-9951463-0
  • 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

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
4579e9d9134ee88a7a896edfcabc863e2e82e557af728eaf391ae4946f07af34		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.xml 1288 bytes
xlm_sheet_01.xml
0101ee9e8c3951ec575bb7566d5eddf13ee538f0fe9782373a93f2413e5887d6		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 1067 bytes
xlm_sheet_02.xml
3f1fe57153abf51373b41e259e14cd7b677ecfec1f43f73b973ae63b3ad3f3c1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml 1332 bytes

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