Office (OOXML) / .XLSM malware analysis — malicious · 8ebebc7af11d460a

MALICIOUS

Office (OOXML) / .XLSM

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

MD5: 4b0474ac07780f4465e4db6767f36c32 SHA-1: 8ade2356b7a4bb3b9e22d620274ecd716a237187 SHA-256: 8ebebc7af11d460ad07f45b922236dc7fa38bfe1776fc938a26636b835aa2c48

130 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File T1105 Ingress Tool Transfer

This XLSM file contains Excel 4.0 macros that leverage dangerous functions like FOPEN, FWRITE, FCLOSE, and EXEC. The macros construct a path to 'C:\ProgramData\YMF.vbs' and then write data to it. Subsequently, it appears to construct and execute 'C:\ProgramData\YMF.exe'. This indicates a downloader or dropper functionality, aiming to write and execute a second-stage 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` `69b7b34456a9685321bd346ed0a27a327823d4d1d28105f6838c9688ef042d2a`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	5541 bytes

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