Office (OOXML) malware analysis — malicious · 940b08ad90bb913a

MALICIOUS

Office (OOXML)

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

MD5: bf1c9b1a3a038c8eb654905342f728b8 SHA-1: 23efc5af0ab0bb701688a0b9fce3cb9fe741be25 SHA-256: 940b08ad90bb913ac69a04ed0959ca70e3f7d9e7ed96bbea49ff3be4564d3b88

190 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample contains critical heuristics indicating the presence of Excel 4.0 macros, including the use of dangerous functions like FORMULA and HALT. The embedded document body reveals these macros are designed to download a DLL payload from 'http://162.248.227.39/first.php' and save it as '..\yeieowur.dll', likely for execution. This indicates a downloader or droppper functionality.

Heuristics 5

Excel 4.0 macro sheet (6 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 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 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 6

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.xml` `cf1825a3b085e5c600f6e09c6c58c7f1fe259e14f9a0915f2ddf106a13735f1c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml	5734 bytes
`xlm_sheet_01.xml` `eb4bc757f510fdbb709e0b0ba07a386090e1c129fe22ab3970899cf68507715f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet2.xml	3904 bytes
`xlm_sheet_02.xml` `a8de137f82b4947672de2fe635459778026bf24dcdbfb1f0cb74494eefd29cdc`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	1468 bytes
`xlm_sheet_03.xml` `b3ceb4b10c63c5884849d461bcfd49965268f16342b5582612850ead81276dd8`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.xml	1624 bytes
`xlm_sheet_04.xml` `ec2494eab5af22ebd0fab7196ed1fdd149d7271871742286d358e3c0d940ad71`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.xml	1693 bytes
`xlm_sheet_05.xml` `f625d4527df6181dc15064a8c07eb18e81a419a66786237111148022b3b8ee10`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.xml	1686 bytes

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