Emotet Office (OOXML) / .XLSM malware analysis — malicious · a12a2d2c6017d2fe

MALICIOUS

Office (OOXML) / .XLSM

37.2 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300

MD5: efcb2a6dec4787d548a3dfce4539c7f8 SHA-1: 385e53815aeeb54a92bad49f52f3cda4df39dd07 SHA-256: a12a2d2c6017d2fe6a161f326d378a134bb75bb54ef7bd6019156473dabc2af7

250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK

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

This XLSM file contains Excel 4.0 macros, indicated by multiple 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_AUTOOPEN_DEFINEDNAME' firings. The 'OOXML_XLM_DANGEROUS_FN' heuristic confirms the use of dangerous functions like FORMULA, which are used to download and execute payloads. The DOC BODY excerpt reveals reconstructed URLs and the use of 'URLDownloadToFileA' via 'rundll32.exe' to download 'besta.ocx'. The ClamAV detection as 'Xls.Downloader.EmotetExcel122100-9913103-0' strongly suggests the Emotet family. The script's intent is to download and execute a second-stage payload from the reconstructed URLs.

Heuristics 6

Excel 4.0 macro sheet (8 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 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.
ClamAV: Xls.Downloader.EmotetExcel122100-9913103-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Downloader.EmotetExcel122100-9913103-0
Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET

Excel workbook contains 11 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 8

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.xml` `7e43fd3a34b9a01e861dfe456c68f67abfb2b8f42dd37b661b6a0dfb8c8fb495`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml	3257 bytes
`xlm_sheet_01.xml` `ceb5adcada0214181e536a8a058cb456fbcfe4a486d29cd185c8117200520be1`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.xml	1365 bytes
`xlm_sheet_02.xml` `8a64aa30d99902ea7a99a9b90b1ee1238a58df11dd8419d899ea7dd6d334096d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet2.xml	1366 bytes
`xlm_sheet_03.xml` `eb9bfe9bdebda540c828894dc4e9149e1ba7a2691d1ed56b3b04fb6d9a36191e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet3.xml	1363 bytes
`xlm_sheet_04.xml` `2758b4ba64fea766c088d247a1498ea08c026fe41c5c21d48ad4f0f8b7be5e57`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet4.xml	1363 bytes
`xlm_sheet_05.xml` `6451df65cc10e1503db4d453a64f73a9026417657722c57f6ed147c8ec6708ac`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet5.xml	1366 bytes
`xlm_sheet_06.xml` `baa175c596711727ab65048b590e8e52a70cdec06148a9d046c2a6286ecdf57f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet6.xml	1365 bytes
`xlm_sheet_07.xml` `e72f152fc995eb1f1ad88257e6ba1c18f0602a7fbede21eb23a670a9c64dfe55`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet7.xml	1365 bytes

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