Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 bb900d4e26377307…

MALICIOUS

Office (OOXML) / .XLSM

75.1 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-14
MD5: 588aecb79f14fb41bd2bcb9947f4ed7d SHA-1: b12da699a361f79dee8773a61370b8c4bf8305e1 SHA-256: bb900d4e263773078bb3555e2ee03574b845fc05cf44b69e36b1dfa110f7879c
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: User Execution: Malicious File T1059.003 Command and Scripting Interpreter: Windows Command Shell

This Excel 4.0 macro-enabled document (XLSM) contains critical heuristics indicating the use of dangerous Excel 4.0 API functions like FORMULA, which are known to be used for downloading and executing payloads. The embedded URLs, such as 'https://aliceefan.com/wp-content/dTDBJDMSb/', are highly suspicious and likely serve as the source for a second-stage payload. The script also attempts to use regsvr32.exe to execute 'rds.ocx' from both System32 and SysWow64 directories, indicating a clear intent to download and run malicious code.

Heuristics 6

  • 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.Emotet03220-9941786-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03220-9941786-0
  • 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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
26edf9bacfee50b5986426c79eb3159c595a38f59b61b257c6666d6dbea79cdc		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3854 bytes
xlm_sheet_01.xml
16728df0c83af9edbca13e7bf934528980971291f8afa9e213237ad5e9c550aa		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1275 bytes
xlm_sheet_02.xml
eb62ea8fd79da591769622356698b97ab3294ef8032cb3ffcd8f29cb5968841e		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1213 bytes

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