Office (OOXML) / .XLSM malware analysis — malicious · 39c47b42df4d66fe

MALICIOUS

Office (OOXML) / .XLSM

44.4 KB Created: 2020-12-07 14:38:21 UTC Authoring application: Microsoft Excel 16.0300

MD5: b777540ad31de24618cb9818debb2fd4 SHA-1: 6e18fab506aefe0e1d1bdbb7bf61963075a4db61 SHA-256: 39c47b42df4d66fe9b9e4cb03f486a6a8a11770010dd6537c55d2899b2e2021a

210 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File

This XLSM file contains embedded VBA macros and Excel 4.0 macros. The critical heuristics indicate that the VBA code utilizes ActiveX events to decode and execute XLM formulas, and that these formulas call dangerous API functions like RETURN. The VBA script attempts to execute a command named 'listP_ab' via Wscript.echo, which is likely a dynamically constructed payload or command. The presence of hidden sheets and the use of XLM macros for execution are common techniques for obfuscating malicious activity and downloading further payloads.

Heuristics 6

VBA ActiveX event runs worksheet-decoded XLM formulas critical OLE_VBA_ACTIVEX_XLM_CELL_STAGER

VBA code attached to an ActiveX/UserForm event reconstructs formula text from worksheet constants using Split/Replace/Mid or character shifting, then executes it through ExecuteExcel4Macro or Run. This is a high-confidence malware stager that hides XLM formula execution in sheet cells; it is not a document-parser CVE.
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.
VBA project inside OOXML medium OOXML_VBA

Document contains vbaProject.bin — VBA macros present
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
- http://schemas.openxmlformats.org/markup-compatibility/2006
- http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac

Extracted artifacts 4

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas` `90d02c3e14283f69e15b3eb80b0e831fd0159245534a40b483bb2ae65874c416`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	1789 bytes
`vbaProject_00.bin` `7d4c595e7350dcdde263dd166042a0ee91b2a84ce9980edb613b096492a4d3bb`	vba-project	OOXML VBA project: xl/vbaProject.bin	18432 bytes
`emf_00.emf` `da935e8d60e93e41bcd7c3fbb1750ef3ac471c3af78afc8945dfbf31eb54a1e1`	ooxml-emf	OOXML EMF part: xl/media/image1.emf	1408 bytes
`xlm_sheet_00.xml` `9434ed12d2419920a533659a4ea2d68e7deb99cf78c946cf9f0abe71dba548eb`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	1092 bytes

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