Office (OOXML) / .XLSX malware analysis — malicious · 35cd91702e758bcd

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: d611760579c4ae6914e4a4c8ff3637e3 SHA-1: 9de32149bcf0fa95598fada209205a3c58c85ca5 SHA-256: 35cd91702e758bcdf0002a645258373323cab8070664fe4fe6687e166905b154

190 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 sample contains Excel 4.0 macro sheets with Auto_Open defined names, indicating it is designed to execute automatically upon opening. The macros utilize dangerous XLM formula APIs like FORMULA.FILL to construct and likely execute commands. The script evidence points to the reconstruction of a URL, suggesting the macro's purpose is to download and execute a second-stage payload from the embedded URLs: https://biopaten.no/xeBP8Oj5/gg.html and https://beartoothkawasaki.com/QJT19jhtwHt/gg.html. The presence of hidden sheets further supports the concealment of 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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