Office (OOXML) / .XLSM malware analysis — malicious · 10f9521a7713fce8

MALICIOUS

Office (OOXML) / .XLSM

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

MD5: 1accdbfdd9094b6e0e16f05e0ff29462 SHA-1: e90eaf516513ffc9772f913071d32709aa73878e SHA-256: 10f9521a7713fce85a618852e7b9f7a3c0e0b3f6eb6b4bbd689ad7e04aed9670

130 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File T1566.001 Spearphishing Attachment

The file is an XLSM document containing Excel 4.0 macros. These macros utilize dangerous functions like FOPEN, FWRITE, and EXEC to construct and write a VBScript file to disk at 'C:\ProgramData\feYfUkkN J yF G d.vbs'. The script then likely executes this payload. The presence of hidden sheets and the use of dangerous XLM functions indicate a malicious intent to download and execute a secondary payload.

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` `0a381642b77beffe8be2d90f886027fb58652aa7ec1e5803e99a05e7c0e61523`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	5943 bytes

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