Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 31b56da1bbc2d192…

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: ac3ffdd9a8d372d37ce2f56e8e675c4b SHA-1: 9485b73905caf18999687f410edb8d72b90d8204 SHA-256: 31b56da1bbc2d19241528d58ac177f88d28a7cb4de49446c7c4a042ee06f7a46
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

This XLSM file contains Excel 4.0 macros, detected as malicious by ClamAV as 'Xls.Downloader.Emotet03221-9941790-0'. The macros utilize dangerous XLM formula APIs to download and execute a payload. Specifically, the script reconstructs URLs such as 'bb2play.com/wzzx/9tamtuJMSndL/' and 'romusreselling.xyz/wordpress/bSX/' to fetch a second-stage payload, likely an .ocx file, and executes it via 'regsvr32.exe'. The presence of hidden sheets further supports the malicious intent.

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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