Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 efaf5895bc451e4e…

MALICIOUS

Office (OOXML) / .XLSM

37.6 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-18
MD5: 4e34c93771073e3c4129db7403e9c427 SHA-1: 236d789b1a62c2f1ec7ae33193b37f0ef1027c79 SHA-256: efaf5895bc451e4ecf7f8e071fa412cddbb9cc1edb67013c5a1c1d65ea1878f5
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: Malicious File T1071.001 Application Layer Protocol: Web Protocols T1059.003 Command and Scripting Interpreter: Windows Command Shell

This XLSM file utilizes Excel 4.0 macros, specifically leveraging the dangerous FORMULA API, to download and execute a second-stage payload. The macros construct URLs from concatenated strings and appear to target multiple domains for payload delivery. The ClamAV detection as 'Xls.Downloader.Emotet03221-9941790-0' strongly suggests an Emotet family infection. The script also attempts to establish persistence by writing to the registry key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\IAccessible2Proxy.

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
193a597cf9347ebbb9d332eb02b3e4aa560f5f6938f1d13ef5649cb957b20db4		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1507 bytes
xlm_sheet_01.xml
8cf9d5b82b850f313d6893a5c0508b35482ae584949aaa5244e60fb5b25b6ef4		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 4239 bytes

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