Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 f4aa4514f89b080d…

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: 126630e226d8818daab2594381bfbff4 SHA-1: 164a3e6f2c4cc2d209ce0bbb8440869463d8961f SHA-256: f4aa4514f89b080d7606c5874f46382ef9da827cc3fe90f88bd83bd8f98dd976
250 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file is an XLSM document containing Excel 4.0 macros, as indicated by multiple critical heuristic firings including OOXML_XLM_MACROSHEET and OOXML_XLM_DANGEROUS_FN. The macros utilize the FORMULA API to construct and execute URLs, such as 'https://aliceefan.com/wp-content/dTDBJDMSb/', which are likely used to download a second-stage payload. The ClamAV detection as 'Xls.Downloader.Emotet03220-9941786-0' strongly suggests the Emotet family. The script also attempts to execute 'regsvr32.exe' with an OCX file from system directories, indicating a download and execution chain.

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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