Malicious Office (OLE) / .XLSX — malware analysis report

Static analysis result for SHA-256 d21ac20e71ee48b1…

MALICIOUS

Office (OLE) / .XLSX

139.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: aa44fdb708ab20e58a8b8369a30bcece SHA-1: e745cb5b26301427cbc674871e10b30873b75f94 SHA-256: d21ac20e71ee48b13384220676a683cb7efd3c1d1d8fcc465540256bb68ea27a
262 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File T1059.001 PowerShell

The file contains Excel 4.0 macros, specifically an Auto_Open macro, which is a critical indicator of malicious intent. The macros are designed to reconstruct and execute URLs, such as "https://canopuseng.in/b/5G1sl6x/". The reconstructed string "SysWow64\Windows\D"&"l"&"lR"&"egister"&"Serve"&"r" suggests an attempt to register a DLL, likely to download and execute a second-stage payload. ClamAV also detected this as a downloader variant.

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.EmotetRed02222-9938635-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Downloader.EmotetRed02222-9938635-0
  • 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 https://canopuseng.in/b/5G1sl6x/
    • http://sesco-ks.com/wp-content/rDARACyF1lDOz9GP1r/
    • http://dev.learncaraudio.com/wp-admin/v6IKIDu90k8C6Y8/
    • http://fastxmfg.com/voluptatum-voluptatum/rh2CNMHNjdgb6/
    • http://sep.dfwsolar.club/hzh3v/c083ujO5b11tuo92/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
f459bbc7010b3c85969ff63ef843cbb5e7e74898bddba8eda2f959641ace8b9e		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 6401 bytes

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