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

Static analysis result for SHA-256 f840af54c53ff3e2…

MALICIOUS

Office (OOXML) / .XLSM

33.6 KB Created: 2021-01-20 10:44:11 UTC Authoring application: 16.0300
MD5: acd2eac5bbcece32cac93280892829cd SHA-1: 95c4411d37764f5a3817cfd80167d312b7de19e7 SHA-256: f840af54c53ff3e231e7da48ecace780f92c2c66c291a96d25e74737d7a2a99e
250 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros that leverage the `RETURN()` function, which is a dangerous API that can call directly into Win32 functions. The `URLDownloadToFileA` function is explicitly called, indicating the macro's intent to download a second-stage payload from a remote location. The presence of hidden sheets and the use of XLM macros suggest an attempt to conceal malicious activity.

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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