IcedID — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 55cc79f882c7dd68…

MALICIOUS

Office (OOXML) / .XLSM

170.5 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 2d34b7102b07de13eb7a46f933e96df7 SHA-1: 71db9b2d9b08b8be286106286f6222ce49a346ef SHA-256: 55cc79f882c7dd687cb16e2a86716c1c2e906de0d16ccf047969c8a4ca4a3f47
240 Risk Score

Malware Insights

IcedID · confidence 95%

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

The sample is an XLSM file containing Excel 4.0 macros, specifically utilizing dangerous functions like FORMULA.FILL, GOTO, RETURN, and EXEC. These functions are indicative of a downloader, capable of executing arbitrary code. The ClamAV detection as 'Xls.Downloader.IcedID' strongly suggests the IcedID family. The embedded URLs are likely sources for the second-stage payload.

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.FILL, GOTO, RETURN, EXEC 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
    • 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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
f7a7d858a289c655913c511b5f5d8782821a8118c456bccdca038cd83fd83627		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 4787 bytes
xlm_sheet_01.xml
ec666c9d225befa7b355659a9f4b1be9fc09d89a108ceccff5430c2c3d528ed9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 2475 bytes

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