SquirrelWaffle — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 164c532643266053…

MALICIOUS

Office (OLE) / .XLSX

247.5 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel First seen: 2021-10-23
MD5: 07c4563b9667fad6b5c9497ced7a3514 SHA-1: 6fc2e8c5193138d7b9c2cd33f71517221ebf61c2 SHA-256: 164c532643266053fc972cc46fe620a62789d3ac7d14a108d20d5e37ed8c3799
262 Risk Score

Malware Insights

SquirrelWaffle · confidence 95%

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

The file contains Excel 4.0 macros with an Auto_Open entry, which is a critical finding. These macros are designed to execute dangerous functions and reconstruct URLs from cell arrays. The reconstructed URLs point to external resources, indicating the macro's intent to download and execute a second-stage payload. ClamAV detection further supports this assessment, identifying the file as a downloader.

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://samtnpy.org/bveCGKTX/ghb.html
    • https://massngo.org/dXKvyKV9v8c/ghb.html
    • https://vathiriyar.org/uy0Tk0keJUr/ghb.html

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
8038cb32870f91f07ba8d77d2b38d0de4989e88a9f0271274f420bb3e000a522		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 11469 bytes

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