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

Static analysis result for SHA-256 112f8c09f8427da4…

MALICIOUS

Office (OOXML) / .XLSX

71.6 KB Created: 2020-12-09 13:54:28 UTC Authoring application: 16.0300
MD5: 592168f1b06bdae1f228c48badb50081 SHA-1: 11899c44eeb3ed1cff77af231d7ec9d0d4021814 SHA-256: 112f8c09f8427da46f5185113c9ab42a7eb7f4eb856daa7c63ff5ebb9a234560
150 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains critical heuristics indicating the presence of Excel 4.0 macros, specifically noting the use of dangerous functions like 'RETURN()'. The VBA script, while obfuscated, attempts to construct and execute a command, likely to download and run a payload. The presence of hidden sheets and the use of dangerous XLM functions suggest a malicious intent to execute arbitrary code.

Heuristics 5

  • 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 4

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
9a7f49d3409500d07ad9b358e4351fad4e4c3ad27f180f62e2491ecd87542cbf		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 1820 bytes
vbaProject_00.bin
c62af521a91c9f8b61a530322fdf287123ee251b20769fbc37e09cabd953922c		 vba-project OOXML VBA project: xl/vbaProject.bin 18432 bytes
emf_00.emf
76f287b1e3251b7e0e5ba27bfb05b35831150cc665de00f9fd2d807e2d2a028d		 ooxml-emf OOXML EMF part: xl/media/image1.emf 1976 bytes
xlm_sheet_00.xml
c163b4b03258d768e20273cba20687877c5c7f5a42a399b21499858bdda3b34e		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 980 bytes

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