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

Static analysis result for SHA-256 b13b959632bf32ae…

MALICIOUS

Office (OOXML) / .XLSM

58.3 KB Created: 2021-01-27 13:28:19 UTC Authoring application: 16.0300
MD5: cdc8faaa9a3bef3cb590b674122b8054 SHA-1: 27b7d2497d439bdc626e2c1bd18dda13a50d3fc0 SHA-256: b13b959632bf32aebf8d1b1106d6bf35afb374c7bfef2aa3fa5b7d20593b3f1f
250 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The `URLDownloadToFileA` function is called from VBA, indicating an attempt to download a second-stage payload. The use of `RETURN()` in the XLM macro sheet is a primitive for executing arbitrary code. The specific functions and API calls suggest a downloader or droppper functionality.

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 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
aac30244719a9ad4905616abf6150e637ea0bb4da5bdac54f5bc4f0cbe02877a		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2737 bytes
vbaProject_00.bin
fd54a0b1c0d23372dcd39e3e43a636b1beea1741a0ee0c73848fa18455c5fefc		 vba-project OOXML VBA project: xl/vbaProject.bin 20992 bytes
xlm_sheet_00.xml
84887edcc31d7128cfb22361727373a9d642c54622a8ee0f177e3c2338de0273		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1095 bytes

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