Office (OOXML) / .XLSM malware analysis — malicious · 2ad46c8101074fde

MALICIOUS

Office (OOXML) / .XLSM

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

MD5: e198f00f1a647ac1ba433e9fef9cbb85 SHA-1: b15fa3972a21acbc3118a8243a965b4f0eaed4e3 SHA-256: 2ad46c8101074fdec26510185eeee98fa0253c06fa87b54b5c15018d6a50970f

130 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1059.003 Windows Command Shell

The sample is an XLSM file containing Excel 4.0 macros. These macros utilize dangerous functions like FOPEN, FWRITE, and FCLOSE to write a VBScript file named 'tSn.vbs' to 'C:\ProgramData\hdm\'. The script is then likely executed, potentially leading to further malicious activity. The presence of multiple dangerous XLM formula APIs and the construction of a file path strongly indicate 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` `05154110085aba7bc5da736f10cc36c1353c9e835fe733c16c3f287cbdc6b126`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	5827 bytes

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