Office (OOXML) / .XLSM malware analysis — malicious · 787d61502a54e3f9

MALICIOUS

Office (OOXML) / .XLSM

34.2 KB Created: 2021-01-19 08:51:14 UTC Authoring application: 16.0300

MD5: ae9ee48b802e572eff66e49458096f34 SHA-1: 31cd58d40729314d6c1b2620a43daefae5cc48fe SHA-256: 787d61502a54e3f9ed7d224bc7084e63e593c3cc50e2a9eddd896192826e6fd2

250 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1203 Exploitation for Client Execution

This XLSM file contains critical Excel 4.0 macros, including the dangerous `RETURN()` function, which can be used to call Win32 APIs. The presence of an `Auto_Open` macro and hidden sheets further indicates malicious intent. The VBA code appears to be obfuscated, but the core functionality likely involves executing the XLM macros to download and run a payload.

Heuristics 7

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: 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.
ClamAV: Win.Malware.Agent-9822772-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Win.Malware.Agent-9822772-0
Auto_Open macro high OLE_VBA_AUTO

Auto_Open macro
VBA project inside OOXML medium OOXML_VBA

Document contains a VBA project — VBA macros present
Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET

Excel workbook contains 2 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
- http://schemas.openxmlformats.org/markup-compatibility/2006
- http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas` `1b70075c55e6cce9aa17d3012fcce1d981fdfb2a4708bd4df1e571205736c985`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	4481 bytes
`vbaProject_00.bin` `2ddc58478f7b917f40ea1f063b28c5b9f6945b9e4e5fa8469fc732d73bf674f6`	vba-project	OOXML VBA project: xl/vbaProject.bin	29696 bytes
`xlm_sheet_00.xml` `5b5dcb2f030adcab65a6222035f9e1adf076e7494a34f1fe990be2faa35a9a03`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	1103 bytes

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