Office (OOXML) / .XLSM malware analysis — malicious · de8496ed6b3b34b3

MALICIOUS

Office (OOXML) / .XLSM

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

MD5: 90d8f3e52af44b5dafa4151c0cfb44c7 SHA-1: 2b2a6793801f675f29794716b7d6585f27638cb5 SHA-256: de8496ed6b3b34b3ed7ca989740397f46cfd313e1b2ed015b8e5f6bd1a92c8a9

130 Risk Score

Malware Insights

MITRE ATT&CK

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

The file is an XLSM document containing Excel 4.0 macros. Heuristics indicate the use of dangerous XLM formula APIs such as FOPEN, FWRITE, FCLOSE, EXEC, and CALL. The macro constructs a file path 'C:\ProgramData\XabfA.vbs' using character concatenation and then likely uses EXEC to run it. This indicates a downloader or dropper functionality, aiming to 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` `5f650e3caf26b50a0695c961a6859411e9729ebea1da405bff61671116bbebec`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	6135 bytes

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