Malicious PDF / .BAK — malware analysis report

Static analysis result for SHA-256 c5263c9242b5da51…

MALICIOUS

PDF / .BAK

224.6 KB Created: 2009-03-12 21:39:34 +08:00 Authoring application: Acrobat PDFMaker 6.0 for Word (via Acrobat Distiller 6.0.1 (Windows))
MD5: f83ba4625d1f79312de78ae4aaa4f122 SHA-1: 304d36de05c38acd1660db14666bfa56789270b6 SHA-256: c5263c9242b5da51c6a75332c473e47a108d40578ad1a6da4c54859006209dfe
174 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell

This PDF file exhibits multiple high-severity heuristic firings related to JavaScript execution, including the use of eval() and String.fromCharCode, indicating obfuscated malicious code. A secondary embedded PDF was also detected with similar suspicious findings. The primary suspicious artifact is an extracted JavaScript file, likely containing the malicious payload. The ML classifier strongly flagged this PDF as malicious. The overall intent appears to be the download and execution of a second-stage payload.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9972

Heuristics 7

  • Secondary embedded PDF body has suspicious static findings critical POLYGLOT_CHILD_PDF_STATIC_TRIAGE
    A valid PDF body was found at a nonzero offset inside another container and its carved contents matched PDF exploit or lure heuristics. This catches polyglots where the top-level magic routes to ZIP/OLE while a PDF reader or downstream parser opens the hidden PDF payload.
  • eval() call high PDF_EVAL
    eval() found — commonly used for obfuscated exploit execution (matched inside decoded stream)
  • Suspicious extracted artifact medium EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • JavaScript action low PDF_JAVASCRIPT
    PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • Embedded JS stream low PDF_JS
    PDF references a /JS stream. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • String.fromCharCode low PDF_FROMCHARCODE
    String.fromCharCode found — used to construct payload strings dynamically. Common in benign JavaScript libraries for codepoint manipulation, so this alone is informational; weaponised use is also caught by the dedicated fromCharCode-stage and exploit-shape rules. (matched inside decoded stream)
  • 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 http://www.w3.org/1999/02/22-rdf-syntax-ns#
    • http://ns.adobe.com/iX/1.0/
    • http://ns.adobe.com/pdf/1.3/
    • http://ns.adobe.com/pdfx/1.3/
    • http://ns.adobe.com/photoshop/1.0/
    • http://ns.adobe.com/xap/1.0/
    • http://ns.adobe.com/xap/1.0/mm/
    • http://purl.org/dc/elements/1.1/

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0024_000.js
e0d35e16815a655c321930374c71d30d7cfd0832aecbef1191b791c223bdd579		 pdf-javascript-stream PDF /JS object 24 at offset 0x7D1 13626 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 2 eval/decoder/string-building token(s). Carved artifact contains 1 long hex-escaped blob(s).
polyglot_child_pdf_off00035f3d.pdf
5a269b165b7c7d9cab7013a9828d3a54efd29fb2b3679cee556e77c3f99cfb91		 polyglot-child-pdf Secondary PDF body inside pdf container at offset 0x35F3D 9042 bytes

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