SquirrelWaffle — Office (OLE) / .XLS malware analysis

Static analysis result for SHA-256 c5cca5c9445e76e4…

MALICIOUS

Office (OLE) / .XLS

258.0 KB Created: 2015-06-05 18:19:34 Authoring application: Microsoft Excel
MD5: c63b437e29a5b4521c75daeea4ab83af SHA-1: bf2bd99bb2b71adea0815ce37484a1353da533a7 SHA-256: c5cca5c9445e76e49f6df0b1eb626e66710f7a13804ab319afd53ca7adddd4ef
302 Risk Score

Malware Insights

SquirrelWaffle · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1204.002 Malicious File Execution: Malicious File

The file is an Excel 4.0 macro-enabled spreadsheet containing an Auto_Open macro. This macro is designed to execute a series of concatenated URLs, which are reconstructed as https://ricardopiresfotografia.com/RpuaNlWy/host.html, https://keysite.com.co/IQ3mbS6EF/host.html, and https://colegiobilinguepioxii.com.co/SYqvKoF4/host.html. This behavior is characteristic of a downloader, aiming to fetch and execute further malicious content. ClamAV detection further supports this assessment.

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.SquirrelWaffle20921-9895790-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.SquirrelWaffle20921-9895790-0
  • Reference to ShellExecute API high SC_STR_SHELLEXEC
    Reference to ShellExecute API
  • 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://ricardopiresfotografia.com/RpuaNlWy/host.html
    • https://keysite.com.co/IQ3mbS6EF/host.html
    • https://colegiobilinguepioxii.com.co/SYqvKoF4/host.html

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_macros.txt
1c0da9705d2c137621f4b1e4afc5cdb9a502214bf2a38375ba5789354cfc2ffb		 xlm-macro oletools.olevba.extract_all_macros (XLM macro listing) 7624 bytes

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