IcedID — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 cff8e3dd7dd27e58…

MALICIOUS

Office (OOXML) / .XLSX

331.5 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 795b83559dff59fb6121a3103e7a5826 SHA-1: 098fcc1e8e3160e89bb96e68ccba0a83dda9dda8 SHA-256: cff8e3dd7dd27e58e8b67ffbaed058d6b849d6d8288031e17be09d9ca2555df1
250 Risk Score

Malware Insights

IcedID · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File

The sample is an Excel file containing multiple Excel 4.0 macro sheets, including an Auto_Open macro. Critical heuristics indicate the use of dangerous XLM formula APIs like FORMULA and REGISTER, which are commonly used to download and execute payloads. ClamAV detection explicitly identifies the file as 'Xls.Downloader.IcedID', confirming the family and downloader functionality.

Heuristics 6

  • Excel 4.0 macro sheet (10 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, REGISTER, 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.
  • ClamAV: Xls.Downloader.IcedID-9f1f1d193a2a2a2b-9951463-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.IcedID-9f1f1d193a2a2a2b-9951463-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 10 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 — context-specific rules above attribute URLs they actually evaluated; this rule lists URLs that were present in the bytes but were not otherwise tied to a specific finding.
    URL http://schemas.openxmlformats.org/spreadsheetml/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/excel/2006/main
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 10

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
f625217fb847b046d42bbedbfc768678a9ca133653762a5a97d60701302827dc
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3496 bytes
xlm_sheet_01.xml
05429996701eacd52396b49a7b542ebf5f54ec159e49392a0fde30360c280f6c
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml 2017 bytes
xlm_sheet_02.xml
c93414afa90d0aed96b0ce72668e15428c1af49ef990d4433b19efa6b27dd697
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet3.xml 2703 bytes
xlm_sheet_03.xml
caf907d21dc38a6bc75aedd846db9e62599779d4c2dbd3f24898f275d22c250a
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet4.xml 1521 bytes
xlm_sheet_04.xml
7667966c8045cbbf1d7c1f279245a5e7c4ac004e5ebe30fbd872010d3792710f
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet5.xml 1791 bytes
xlm_sheet_05.xml
c2e30072b0b55de845ae0cc0cf580b57d25538df7bd72d890703ffb59bd466f3
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet6.xml 1667 bytes
xlm_sheet_06.xml
4a0db02a3673bae10855faec06cd35685ff751631b0072a271b38d935beecf95
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet7.xml 1735 bytes
xlm_sheet_07.xml
a0c80460b9f4e41cc5c80274d1c193d030f8b4e954b0aa51ef669e0af14e35d8
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet8.xml 1679 bytes
xlm_sheet_08.xml
1c52474b1448a0ffd9d21d1a06b05ada2668f4c15ffc52265026119f5dff69ca
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet9.xml 1611 bytes
xlm_sheet_09.xml
6dabbcd902efa205f4f62712457f79144c15a373fe7c951a3cc043bb5817e545
xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1790 bytes