Office (OOXML) / .XLSM malware analysis — malicious · 04341658994d1706

MALICIOUS

Office (OOXML) / .XLSM

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

MD5: fb01344980b58ecb3e0374df47688fc8 SHA-1: 5f23e7357657cf91634faa2fb8fd4c7c30cfcb09 SHA-256: 04341658994d17064801b9d675f01d415a01610b0ba6d6b04e604dd2dfd8e613

130 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file is an XLSM document containing Excel 4.0 macros. These macros utilize dangerous functions like FOPEN, FWRITE, and EXEC to construct a file path 'C:\ProgramData\YCI GbKkF XyNp.vb' and then likely execute it as 'C:\ProgramData\YCI GbKkF XyNp.exe'. The presence of hidden sheets and the use of direct Win32 API calls via XLM formulas indicate a malicious intent to download and execute a 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` `9f12a2bb49d96e578ca835719ecaca09f40c3353d25d024538a914c82a286071`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	6043 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.