Emotet — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 1c5adfae1073ecb8…

MALICIOUS

Office (OLE) / .XLSX

104.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: ee54eab5f89c57f8329d1c0bfb3d1912 SHA-1: df4a2adeebe0a239dcf56915602fab1ca2758eb0 SHA-256: 1c5adfae1073ecb849da920498cb13ba69092085c749b3106f504ef8172c973f
262 Risk Score

Malware Insights

Emotet · confidence 95%

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

The presence of an Excel 4.0 Auto_Open macro, identified by critical heuristics, indicates the file is designed to execute automatically upon opening. The macro utilizes dangerous functions like RUN and reconstructs URLs from cell arrays. These URLs are likely used to download and execute a second-stage payload, consistent with Emotet's typical delivery mechanism. The reconstructed string '"h"&"tt"&"p://c"&"ab"&"le"&"eq"&"uip"&"me"&"nt"&"man"&"ag"&"em"&"en"&"tr"&"et"&"ur"&"ns.c"&"o"&"m/w"&"p-a"&"dm"&"i"&"n/JPi"&"vi"&"zx"&"mi"&"wo"&"9A"&"5Ow"&"ys/"' is a clear indicator of this malicious intent.

Heuristics 6

  • Excel 4.0 Auto_Open defined name critical OLE_XLM_AUTOOPEN_DEFINEDNAME
    oletools recovered an Auto_Open / Auto_Close entry from an Excel 4.0 macro sheet. The raw BIFF name can be tokenized or partially opaque to byte-string checks, but the recovered macro listing confirms the workbook has an XLM auto-execution entry.
  • XLM Auto_Open with dangerous formula APIs critical OLE_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and dangerous XLM formula APIs that can invoke programs, write files, or transfer control without VBA.
  • URL reconstructed from XLM cell array (5 URLs) critical OLE_XLM_CELL_ARRAY_URL
    Excel 4.0 macro sheet stages its payload URL across the BIFF8 Shared String Table (one quoted-char SST entry concatenated with & at runtime) or across individual numeric cells (one ASCII charcode per cell). The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF8 record stream and decoding SST entries plus LABELSST/RK/NUMBER cells.
  • ClamAV: Doc.Downloader.EmotetExcel02220-9938626-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.EmotetExcel02220-9938626-0
  • Excel 4.0 (XLM) macro sheet present medium OLE_XLM_AUTOOPEN
    Workbook contains an Excel 4.0 macro sheet sub-stream — XLM is rarely seen in modern legitimate workbooks and was a major Office malware vector during 2020-2022.
  • 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://cableequipmentmanagementreturns.com/wp-admin/JPivizxmiwo9A5Owys/
    • http://novawedevent.com/tmp/PA0rBwFszIpy/
    • https://www.altasolutions.asia/myfiles/myB984EnOlSJJ4b9/
    • https://www.sanskriticreations.net/wp-admin/iGdDEvnMusgGlIoaR/
    • http://kiwibeautyhouse.com/wp-includes/js/tinymce/themes/qzutpR1kPAPp54/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
be1ac9f30af65ef180310243cbba4a51ea41ae015d1d5e2b649c82e30f6f4b5c		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6365 bytes

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