Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 818aad6fc630d503…

MALICIOUS

Office (OOXML) / .XLSM

33.0 KB Created: 2015-06-05 18:17:20 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-16
MD5: c330ee50ac3be566d2adbf05c9e38f19 SHA-1: 1ec8d2732282985c31fe90c797a3965fca99760f SHA-256: 818aad6fc630d5034acf0e6f238ece096d010b1e88770e599cabd5a20891440d
290 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1218.010 System Binary Proxy Execution: Regsvr32

This Excel 4.0 macro-enabled document (XLSM) contains critical heuristics indicating the use of dangerous XLM formula APIs like FORMULA, CALL, EXEC, and REGISTER. The document body and extracted scripts reveal that these functions are used to construct and execute a command involving regsvr32.exe, which then downloads and executes a payload from one of the embedded malicious URLs. The ClamAV detection further confirms this as Emotet.

Heuristics 7

  • Excel 4.0 macro sheet (1 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.Emotet03222-9941788-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03222-9941788-0
  • 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 https://casache.com/web/n3jxwXXwa/
    • http://ccalaire.com/wp-admin/d1pGRa0X/
    • http://careerplan.host20.uk/images/Ls/
    • https://azsiacenter.com/js/sOhmiosLJOgwaP6i5nln/
    • https://www.blessingsource.com/blessingsource.com/rFQ0Ip6lQXXK/
    • http://cdimprintpr.com/brochure2/A9NmYDndZ/
    • http://ausnz.net/2010wc/odSi5tQKkCIXEWl9/
    • 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 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
db0a59e4a9d5995912532cf04297a579397bf9cc37c53dfcf4ddd0de285133c8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 4122 bytes

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