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

Static analysis result for SHA-256 fd2cc0c858b7b92b…

MALICIOUS

Office (OOXML) / .XLSM

40.6 KB Created: 2021-03-15 12:53:22 UTC Authoring application: Microsoft Excel 16.0300
MD5: 1573b4ec83ac67af060289a37896b0c9 SHA-1: b95d31d6b268f4382c438ba8cdb2d6fae9e23572 SHA-256: fd2cc0c858b7b92b32d86f7bb8a48d56798667a2bc7e75fe44f074178ea3a0d6
208 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros. Critical heuristics indicate the use of dangerous XLM formula APIs like CALL and EXEC, and specifically URLDownloadToFile, which are commonly used to download and execute second-stage payloads. The presence of hidden sheets further suggests an attempt to conceal malicious activity. While no specific family is identified, the technique points to a downloader malware.

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 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://www.w3.org/1999/02/22-rdf-syntax-ns#
    • http://ns.adobe.com/xap/1.0/
    • http://purl.org/dc/elements/1.1/
    • http://ns.adobe.com/photoshop/1.0/
    • http://ns.adobe.com/xap/1.0/mm/
    • http://ns.adobe.com/xap/1.0/sType/ResourceEvent#
    • 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
4b64436373195a80360bde6a497c3849be16c627bf6047e3d2c7a46b7e1f2b1a		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3014 bytes
vbaProject_00.bin
50872f4d7224548feb45a6fc713cce2baa2385de5567cfe3c75cede41973f47a		 vba-project OOXML VBA project: xl/vbaProject.bin 24576 bytes
xlm_sheet_00.xml
51d5ceb69c668d371a4c9bdae8ac666f1ffe5283372066c032a6959a65a45674		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 953 bytes

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