SquirrelWaffle — Office (OLE) / .XLS malware analysis

Static analysis result for SHA-256 75b180072fbde634…

MALICIOUS

Office (OLE) / .XLS

247.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: e82dbcacafa13747998191fdc23796ef SHA-1: 4fa8c0f14c16faf7b8a97e55ad5dd49bb7181596 SHA-256: 75b180072fbde634be99159839b49ccb2ca91ae37b79bb06a1c0f294fc3d341c
262 Risk Score

Malware Insights

SquirrelWaffle · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The file is an Excel spreadsheet containing Excel 4.0 macros, specifically an Auto_Open macro that executes dangerous functions. The macros reconstruct and access three URLs, indicating a downloader functionality. ClamAV also identifies the file as 'Xls.Downloader.SquirrelWaffle'. The reconstructed URLs are the primary indicators of compromise.

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 (3 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: Xls.Downloader.SquirrelWaffle1021-9903731-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.SquirrelWaffle1021-9903731-0
  • 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://rickcovell.net/BuQQdjLrrO19/li.html
    • https://networktmg.com/ryrwQGN3wPpT/li.html
    • https://thamilanda.co.in/fui6yOqX0Wyb/li.html

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
3a2ce73613c18f75b993feb272be8136f11b65a1fb5c2694c0440e8107f1f8a2		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 11483 bytes

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