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

Static analysis result for SHA-256 4840443a33395062…

MALICIOUS

Office (OOXML) / .XLSM

33.6 KB Created: 2021-01-20 10:44:11 UTC Authoring application: 16.0300
MD5: 246c352d27fb02c6daf4bb28647b285f SHA-1: d89273f381711142b75bbb495a876a636b674050 SHA-256: 4840443a33395062157663a7c4867ee0fcf045db025470b700da29fba3ef65d9
250 Risk Score

Malware Insights

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

This XLSM file contains an Auto_Open macro and utilizes Excel 4.0 macros, specifically the RETURN function, to download and execute a second-stage payload. The presence of the URLDownloadToFileA API call in the VBA script strongly indicates the intent to fetch and run external content. The document body is heavily obfuscated and does not provide direct clues to the user-facing lure.

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 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
a48e3141aeaa84a95aed2b2bcc68cd584cada5ecacc199ab111341dd9685e8d4		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3337 bytes
vbaProject_00.bin
3fd0859da5a9c4e06952395eae036ffd0e59972d6c16106e949123c30bd423bf		 vba-project OOXML VBA project: xl/vbaProject.bin 24064 bytes
xlm_sheet_00.xml
e7be2ee22fecbaafeca0deb81ce847193431ba86d9a6337d6de3efdeba838f99		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1172 bytes

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