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

Static analysis result for SHA-256 21a292df6f84eee0…

MALICIOUS

Office (OOXML) / .XLSM

114.2 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: a209e8ecdcbcc038383b8cdd2bffe997 SHA-1: 75d4e6b70b524c8fcb7963344a132e510241174b SHA-256: 21a292df6f84eee00f59bba007144be1ebf516e84ead9ca4b2097084710cdf7a
188 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros, which are known to be used for malicious purposes. The critical heuristic 'OOXML_XLM_DANGEROUS_FN' indicates the use of dangerous XLM formula APIs like CALL and EXEC, which are typically used to download and execute payloads. The presence of an Auto_Open macro further suggests automatic execution upon opening the document. The extracted URLs are highly suspicious and likely serve as the source for the second-stage payload.

Heuristics 6

  • 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.
  • Dangerous XLM formula APIs: FORMULA, HALT, GOTO, REGISTER, 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.
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_Open macro
  • VBA project inside OOXML medium OOXML_VBA
    Document contains vbaProject.bin — VBA macros present
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 3 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://91.211.91.81/44313,6048108796.dat
    • http://5.34.179.36/44313,6048108796.dat
    • http://45.153.229.23/44313,6048108796.dat
    • 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 5

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
aa10abebc3ece39bf198cf3383ccb30417606e0a98d60e87747026c15426213c		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2437 bytes
vbaProject_00.bin
c273c0ba9b123bfd6c5297a7692bdade93c1afc5139260c65963114883a46fd3		 vba-project OOXML VBA project: xl/vbaProject.bin 23552 bytes
xlm_sheet_00.xml
665f6c9f9b4a972fb7c9cd862f5d81f8391866e0188d24c7f028f17a82f6de37		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 4505 bytes
xlm_sheet_01.xml
c842664d4adfbab64cc38d3d12f48bc3fe942196965e9c614671ea94f3e6afd5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 2129 bytes
xlm_sheet_02.xml
10c797d7a3c632796484bdf562cdd2d33c46d8d630def0609945fce50d2eff68		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.xml 1949 bytes

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