Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 991f7ad9c45a60bc…

MALICIOUS

Office (OOXML) / .XLSM

35.6 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-21
MD5: 6b4b6782dee0eba8a47661a48bc4e193 SHA-1: b09d0b1f6ced2dfd8875f2c7f0fc386f73cf8afc SHA-256: 991f7ad9c45a60bc8c1eae61a9ba1fef07fedfa8bd66303292c27bff97ad63be
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1059.001 Command and Scripting Interpreter: PowerShell T1204.002 Malicious File Execution: Malicious File T1059.003 Command and Scripting Interpreter: Windows Command Shell

The sample is an XLSM file containing Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous functions like FORMULA to download payloads from multiple URLs, including 'bb2play.com/wzzx/9tamtuJMSndL/'. The ClamAV detection as 'Xls.Downloader.Emotet03221-9941790-0' strongly suggests an Emotet family attribution. The script also attempts to execute 'regsvr32.exe' and constructs a '.ocx' file extension, indicating a downloader pattern.

Heuristics 6

  • Excel 4.0 macro sheet (2 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.Emotet03221-9941790-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03221-9941790-0
  • 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://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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
56299d8024c4f1ac82a7522c7ead08f39677c0bae82297826862fce76df69744		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1495 bytes
xlm_sheet_01.xml
8e2616826469cdb87cf1c4eb49e8c201b264eceb93468f26315db51abb9ca50d		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 4178 bytes

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