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

Static analysis result for SHA-256 55cbb43aad59d149…

MALICIOUS

Office (OOXML) / .XLSM

30.2 KB Created: 2021-01-21 10:44:11 UTC Authoring application: 16.0300
MD5: d89d70ee6809ef93910bfbf10c4caf94 SHA-1: 5e8d4db8464fd6d427d5987ae6cb017ceac13839 SHA-256: 55cbb43aad59d149ba4bc06684771b5d87a3f570da165437c4d07d442d4b8db7
250 Risk Score

Malware Insights

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

This XLSM file contains 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 RETURN, which can be used to download and execute payloads. The VBA script also contains a call to URLDownloadToFileA, further supporting the payload download functionality. The presence of hidden sheets suggests an attempt to conceal malicious activity.

Heuristics 7

  • URLDownloadToFile in VBA critical OLE_VBA_DOWNLOAD
    URLDownloadToFile in VBA
  • Excel 4.0 macro sheet (1 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: RETURN 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://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
macros.bas
85d983da44a5c30a66b5f1e258fa2a79809b3a9aa746ee790d6c7541daf989d2		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3348 bytes
vbaProject_00.bin
24385221538d495e34c8714dc1a4a4ad24a3f81723e33b84f994b2230c005b7b		 vba-project OOXML VBA project: xl/vbaProject.bin 26112 bytes
xlm_sheet_00.xml
3844a482afa6ad8c833ba0510231dcfbe9a8afcaeea3283a7619e8a70ac99183		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1174 bytes

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