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

Static analysis result for SHA-256 5b0c10ba59b492ce…

MALICIOUS

Office (OOXML) / .XLSM

34.2 KB Created: 2021-03-01 12:21:59 UTC Authoring application: Microsoft Excel 16.0300
MD5: 574dc44b4b6d1d779fac7b050f0fcbcf SHA-1: 55ca382219fcca072c98a2541b0f5b96e5241d72 SHA-256: 5b0c10ba59b492cea697932d0285833bf8b76d27e52b682560faf7925a72d937
210 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros and VBA code. The VBA macro utilizes the URLDownloadToFileA function from urlmon to download a second-stage payload from an embedded URL. The presence of dangerous XLM formula APIs like RETURN further indicates malicious intent to execute arbitrary code.

Heuristics 6

  • 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.
  • VBA project inside OOXML medium OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 1 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
8a974090e34b01296ac86575d647b594fe49413bb638d4b7685e9d37fb66da1f		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2702 bytes
vbaProject_00.bin
55f6305f17adeee33a63043714c7d7492bcb5dc38a0db661143bea7eb6e9ea6c		 vba-project OOXML VBA project: xl/vbaProject.bin 20992 bytes
xlm_sheet_00.xml
c05631a0df71609a4d5e5ff00c50349f438558aa33730b995c651d0e3f25def3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 989 bytes

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