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

Static analysis result for SHA-256 b721618810b06ed4…

MALICIOUS

Office (OOXML) / .XLSM

115.8 KB Created: 2021-02-01 13:14:01 UTC Authoring application: 16.0300
MD5: d3355679c2cc488cf1a4c2c91ffc6bb3 SHA-1: 2a0b6bf0c8afb71437fcd1cd97a52bf249138891 SHA-256: b721618810b06ed4089d1469fc5c5b37be1a907fc1ae14222f913c6e2b0001c2
210 Risk Score

Malware Insights

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

This malicious XLSM file utilizes Excel 4.0 macros, a technique that bypasses traditional VBA security warnings. The critical heuristic 'OOXML_XLM_DANGEROUS_FN' indicates the use of dangerous XLM formula APIs like RETURN, which can directly call Win32 functions. The VBA script contains a declaration for 'URLDownloadToFileA' from 'urlmon.dll', confirming its intent to download a payload from a remote source. The presence of hidden worksheets further suggests an attempt to conceal malicious activity.

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
77e60d2aba598abe4cbec11e550f7780203907bf7dc338bc59e6d582520adf9b		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3478 bytes
vbaProject_00.bin
d81ff3f1e204ce666d0bf4d41d81950c38b8a4e7e66cf341cd83db6aa07b8e75		 vba-project OOXML VBA project: xl/vbaProject.bin 22528 bytes
xlm_sheet_00.xml
e9501eb5dfcb8de2bfa22fda5e2388a5766e0b21109b186c0939cf8b4c118007		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1092 bytes

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