Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 f8a8588a7a3cf9a2…

MALICIOUS

Office (OOXML) / .XLSM

43.6 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-09
MD5: 2d018b37feeb7644dcfdf9ae17b1ed65 SHA-1: 41bafd97e2e91d96464717af475050a81331e278 SHA-256: f8a8588a7a3cf9a22758519cf7ece49dfede6aec3670e7a558f8dcd2547a7cbc
290 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1218.010 System Binary Proxy Execution: Regsvr32 T1059.005 Command and Scripting Interpreter: Visual Basic T1105 Ingress Tool Transfer

The sample is an XLSM file containing Excel 4.0 macros, identified by the 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_DANGEROUS_FN' heuristics. The macros utilize the FORMULA API to construct and execute commands, specifically calling 'regsvr32.exe' to download and run a payload from one of the embedded URLs. The ClamAV detection as 'Xls.Downloader.Emotet03221-9941299-0' strongly suggests the Emotet family. The reconstructed command line indicates the use of regsvr32.exe to download from a URL.

Heuristics 7

  • Excel 4.0 macro sheet (3 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.Emotet03221-9941299-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03221-9941299-0
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 5 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://matskigroup.com/wp-admin/nqGatgYyNskXXqEnJw/
    • http://akbakan.com/aQonQ0Rc/
    • http://cabinetcecaf.com/wp-admin/DhqUy/
    • https://cloud-ci.online/backup/dBsIP/
    • http://safecampus.net/wp-includes/YUeG3uumtePP/
    • http://hippocrates-poetry.org/10th-annual-hippocrates/uS0IeOAAuoQ7NP9cm/
    • http://digidist.com/y3/PfakjJB/
    • 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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
45360b765089a5d5456631606a414b3854a3e41bf55aab6d0866eb95d5f29d8a		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 4037 bytes
xlm_sheet_01.xml
6f5cdc5224e3f5d34a78074ca17d0580c3ce9003511ea3ebd2d1242a66f92a09		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1276 bytes
xlm_sheet_02.xml
078006edcec633560dee822f011405034d4936f79daa7b629f378bfbf28e1ba1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1152 bytes

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