SquirrelWaffle — Office (OLE) / .XLS malware analysis

Static analysis result for SHA-256 e5b3903d52e72c85…

MALICIOUS

Office (OLE) / .XLS

240.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: d3ea4c6db1a11ff428c6cad9ef601adf SHA-1: 9f2f2ce96a313a22333fb7fca87ff6022a68d008 SHA-256: e5b3903d52e72c858dfbbdfce5da0ab3d5e9d1771ad213486fc8356928596281
270 Risk Score

Malware Insights

SquirrelWaffle · confidence 95%

MITRE ATT&CK
T1059.005 PowerShell T1059.001 PowerShell T1204.002 Malicious File T1566.001 Spearphishing Attachment

The file is an Excel 4.0 macro-enabled spreadsheet. Heuristics indicate the presence of an Auto_Open macro that utilizes dangerous functions, specifically the RUN function, to execute code. The macro reconstructs and references three URLs, which are likely used to download and execute a second-stage payload. ClamAV detection further confirms this as SquirrelWaffle, a known downloader.

Heuristics 7

  • 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.
  • VBA project contains no executable statements low OLE_VBA_MACROS
    Document contains a VBA project, but extracted modules only contain attributes/options/comments and no executable statements.
  • 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://onlineyogacourse.org/5hgP7n5nTC/a.html
    • https://rabedc.com/msdcluV8y5nf/alf.html
    • https://partiuvamosviajar.com/xYIJTUcGxvF1/alfo.html

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
a9f717d61a965190fe37a142f3f1f2cfd5539047c3ac8ee6515684707e3fea75		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 11249 bytes
macros.bas
4834da2e5d17715a6ad94ead340f61ee67f48a6c0ffbdc55b2533a7039596c85		 vba-macro oletools.olevba.extract_macros (decoded VBA source) 1522 bytes

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