Office (OOXML) / .XLSM malware analysis — malicious · 9077b976eda8d9e6

MALICIOUS

Office (OOXML) / .XLSM

139.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: c57e62366a298fff9d449a313243a71f SHA-1: 95f7b84aba9fbd6cfefd613bd71875f3a4fd81c6 SHA-256: 9077b976eda8d9e62a7f6f76e916fd4f68413ae86c20be72bb70232122655d51

130 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

The sample contains Excel 4.0 macros that leverage dangerous functions like FOPEN, FWRITE, and FCLOSE to construct and write a VBScript file to disk. The reconstructed path for this file is 'C:\Program Files\Common Files\System\a\lxU\ppu\Prq\vbs\Lj\y.vbs'. The macros also contain an ALERT function that appears to be part of the script execution flow, potentially indicating an error or a step in the payload delivery. The use of these functions and the creation of an executable script strongly suggest a downloader or dropper functionality.

Heuristics 4

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: FOPEN, FWRITE, FCLOSE, EXEC, 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.
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://schemas.openxmlformats.org/spreadsheetml/2006/main
- http://schemas.microsoft.com/office/excel/2006/main
- http://schemas.openxmlformats.org/officeDocument/2006/relationships

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.xml` `8ac363647ac8c35a572e10bba4502950973c9940ab35ce10ddd6e855df7f6965`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	5910 bytes

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