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

Static analysis result for SHA-256 8b1203e7ff8ead64…

MALICIOUS

Office (OOXML) / .XLSM

85.8 KB Created: 2021-02-01 10:09:39 UTC Authoring application: 16.0300
MD5: 947a7bffc14cbf99a733cf80b08fbecf SHA-1: 10186c7b0bf23fd6c76a0f529d4d918dfc913987 SHA-256: 8b1203e7ff8ead64a388e8000955871b931202a9fd56ba339de65b01628fff6b
210 Risk Score

Malware Insights

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

This Excel macro-enabled document (XLSM) utilizes Excel 4.0 macros, which are known for their ability to execute arbitrary code and download payloads. The heuristic firings indicate the use of dangerous XLM formula APIs like RETURN, and the VBA code explicitly calls URLDownloadToFileA. This suggests the primary intent is to download and execute a second-stage payload from a remote location. The document body content is heavily obfuscated and appears to be a jumbled string, likely containing encoded URLs or data used by the macros.

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 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
e1818214fe515a79cf059f38d797e2936d844799f9b994a7350225d017873477		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3524 bytes
vbaProject_00.bin
9c154d3efde4dcd0754240e3d6ad91b2b706961edac2319aa5ef1180a4447565		 vba-project OOXML VBA project: xl/vbaProject.bin 23040 bytes
xlm_sheet_00.xml
201f5a92efc753d99ef96af4994a292bf69c665334733ad8c10b7b4a87ca19ea		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1094 bytes

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