IcedID — Office (OOXML) malware analysis

Static analysis result for SHA-256 b5fd10f13fad8e15…

MALICIOUS

Office (OOXML)

184.5 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: bc3403753237998951f81bab4b17215e SHA-1: a7a494b82442cd5f9dcdc614995a01bf7ec4d9a1 SHA-256: b5fd10f13fad8e15d07b878be13e8d8dfb2e2e215002a75c4518d2401a735596
242 Risk Score

Malware Insights

IcedID · confidence 95%

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

The file contains critical heuristic firings indicating the presence of Excel 4.0 macros, including dangerous functions like CALL, EXEC, and FORMULA, which are used to download and execute payloads. The macro explicitly calls the URL 'http://fourstars.cyou/1.php' to download a DLL named '91919.dll' and then executes it using 'regsvr32'. This behavior is consistent with the IcedID malware family, which often uses macro-enabled documents for initial infection.

Heuristics 5

  • Excel 4.0 macro sheet (2 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 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://fourstars.cyou/1.php
    • 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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
d3df3d0996b09806e232547bf408659955ac33ea252003ebc11e0fb5e8bd0cc5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml 1252 bytes
xlm_sheet_01.xml
dcf92c20099b47309d75331e9c53f83a546133e74ba138dee92517f465b268e3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 1408 bytes

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