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

Static analysis result for SHA-256 fa8ed75cfc69a06c…

MALICIOUS

Office (OOXML) / .XLSM

30.2 KB Created: 2021-01-21 10:44:11 UTC Authoring application: 16.0300
MD5: a47b6adc87b8000c91a706d3c5ed540f SHA-1: 5337c9cd3d3813178bd5e7d1e1334ab973bdbb3f SHA-256: fa8ed75cfc69a06cf1e809531f7371b5c75fd480339ae65568785b76387ceaa0
250 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The `RETURN()` function in the XLM macro sheet, combined with the `URLDownloadToFileA` API call in the VBA code, indicates that the macro is designed to download and execute a second-stage payload from a remote location. The presence of hidden sheets and the use of dangerous XLM formula APIs further support this assessment.

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
85d983da44a5c30a66b5f1e258fa2a79809b3a9aa746ee790d6c7541daf989d2		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3348 bytes
vbaProject_00.bin
24385221538d495e34c8714dc1a4a4ad24a3f81723e33b84f994b2230c005b7b		 vba-project OOXML VBA project: xl/vbaProject.bin 26112 bytes
xlm_sheet_00.xml
3844a482afa6ad8c833ba0510231dcfbe9a8afcaeea3283a7619e8a70ac99183		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1174 bytes

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