Office (OOXML) / .XLSM malware analysis — malicious · 8e5805c72e7234c6

MALICIOUS

Office (OOXML) / .XLSM

46.6 KB Created: 2020-12-02 14:50:06 UTC Authoring application: Microsoft Excel 16.0300

MD5: 4192644d7cba3e64d003ef7a621776b5 SHA-1: 0538dcc0ea64eb6e2b863b088de1c71399a2e645 SHA-256: 8e5805c72e7234c6b271487e95aeb12a11e65748bfa1af297b5aeee727bebd00

218 Risk Score

Malware Insights

MITRE ATT&CK

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

This XLSM document contains Excel 4.0 macros that are designed to execute a payload. The VBA code triggers an ActiveX event which in turn executes XLM formulas. These formulas utilize dangerous APIs like RETURN to call into Win32 functions, likely to download and execute a second-stage payload. The reconstructed string 'Kij_roo' is used as a name for a worksheet, which is then executed, indicating a dynamic execution path. The presence of hidden sheets and call-to-action shapes further supports a malicious intent to trick the user into enabling macros and initiating the payload execution.

Heuristics 7

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
Call-to-action shape / download button low OOXML_DOWNLOAD_SHAPE

Document drawing contains a call-to-action phrase ('Click Here', 'Download Now', etc.) inside a shape or text box — a common visual lure used to trick users into enabling macros or visiting a malicious URL
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` `aa9ea638a3c943e41c8bb2745c0c052a5779da85b0f7e742f1e98e586f2dec22`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	1617 bytes
`vbaProject_00.bin` `37efdcde3786b3fff02eb34e04d3fff1b666eb61c48e766bbaf61763edd7c927`	vba-project	OOXML VBA project: xl/vbaProject.bin	19456 bytes
`emf_00.emf` `6bb4422277f2c519e18c88b5df3fcd468514bbd8dcc596bcdeccec768b255322`	ooxml-emf	OOXML EMF part: xl/media/image1.emf	2352 bytes
`xlm_sheet_00.xml` `bc9c6ebf0fd320628e241812b20c7929365b4e65eb917fa20596b9adfe330f8f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	957 bytes

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