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

Static analysis result for SHA-256 176eaf6e286fc4da…

MALICIOUS

Office (OOXML) / .XLSM

79.8 KB Created: 2021-02-10 12:29:58 UTC Authoring application: 16.0300
MD5: b75d5208179a72bbdedd81354e372ffa SHA-1: f431cd998a5b8d4e1d5c20473d8dd57b7a1defb0 SHA-256: 176eaf6e286fc4dae986a46d712f92ab08ca051ab4cbd70db9e15cc4ebfc7815
210 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The heuristics indicate the use of dangerous XLM formula APIs like RETURN, and the VBA code includes a call to URLDownloadToFileA, suggesting it's designed to download and execute a second-stage payload. The presence of hidden sheets further supports the malicious intent.

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 a VBA project — VBA macros present
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 4 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
93dd6a04e1c8847dc3bcb46aa910b0b6f137bb36204e9deaa7e2933cbbc93734		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3924 bytes
vbaProject_00.bin
d5a1287bfac2e7cf5777d15e3599bb3214f5463a0615a612e8d2ec1b57bd519f		 vba-project OOXML VBA project: xl/vbaProject.bin 25600 bytes
xlm_sheet_00.xml
e4d5ed32618eb4dd5e368d0c0a92dde4c221eb4d71d635dcc1ba0e4cf3875218		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1055 bytes

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