Office (OOXML) / .XLSX malware analysis — malicious · 45ee7aa84e1ba8f2

MALICIOUS

Office (OOXML) / .XLSX

158.3 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 16.0300

MD5: 3712bb0266b75ed1954a85201c2aba21 SHA-1: b7ce0c2735bb83de3d10a1a6297c45a681b6c6c9 SHA-256: 45ee7aa84e1ba8f2a56b8ac4a296b297b3f9a4f61e313b6336925eaee3b1180d

190 Risk Score

Malware Insights

MITRE ATT&CK

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

The sample is an Excel file containing Excel 4.0 macros, indicated by the 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_AUTOOPEN_DEFINEDNAME' heuristics. The 'OOXML_XLM_DANGEROUS_FN' heuristic confirms the use of dangerous functions like FORMULA, HALT, and FORMULA.FILL, which are used to download and execute payloads. The embedded URLs 'https://biopaten.no/xeBP8Oj5/gg.html' and 'https://beartoothkawasaki.com/QJT19jhtwHt/gg.html' are likely sources for these payloads. The hidden sheet heuristic suggests an attempt to conceal malicious activity.

Heuristics 5

Excel 4.0 macro sheet (5 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.
Excel 4.0 Auto_Open defined name critical OOXML_XLM_AUTOOPEN_DEFINEDNAME

Workbook defines _xlnm.Auto_Open or _xlnm.Auto_Close while containing an XLM macro sheet. This is the OOXML/XLSB auto-execution shape for Excel 4.0 macros.
Dangerous XLM formula APIs: FORMULA, HALT, FORMULA.FILL 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 https://biopaten.no/xeBP8Oj5/gg.html
- https://beartoothkawasaki.com/QJT19jhtwHt/gg.html
- 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
- http://schemas.microsoft.com/office/spreadsheetml/2014/revision
- http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
- http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
- http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 5

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.xml` `15fbfe55b20413f92e6ae6dcaa5199ef4834995471413702ff1b1894f486343d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml	11346 bytes
`xlm_sheet_01.xml` `01be081374433318ab060c7d9534b134366d414e43d756214d58deb1a7557a22`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml	1807 bytes
`xlm_sheet_02.xml` `4942d78e9a4c26c9352582ba044fbdd7b5e434ac67308d3cb59b8725b48e9b99`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet3.xml	1777 bytes
`xlm_sheet_03.xml` `a6863ce46a6a991745232b05bc1b5af380056ae05155ba24221669ae920dc1d9`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet4.xml	1460 bytes
`xlm_sheet_04.xml` `7a65a9a19541a783d2364e0cc237ab353fd49b12ac69aaaae5e6996c7d787d37`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet5.xml	1558 bytes

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