Malicious PDF — malware analysis report

Static analysis result for SHA-256 71dd53a4cc3b488a…

MALICIOUS

PDF

37.7 KB
MD5: fc5a395f60c361f6b3e69a420f7a7bcc SHA-1: 3e89daf0ec6fbd439d58825aa6d04cee6eb4eee4 SHA-256: 71dd53a4cc3b488a6f84ed4f21790b4a5b2c58f8c81149aa97f021fd922ec47f
186 Risk Score

Malware Insights

MITRE ATT&CK
T1059.007 JavaScript T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The sample is a PDF file containing obfuscated JavaScript. The JavaScript uses `String.fromCharCode` and concatenates various strings to construct a URL, likely for downloading a second-stage payload. The presence of PDF-specific exploit heuristics and the ML classifier strongly indicate malicious intent. The embedded Flash object also suggests a potential exploit vector.

Machine Learning

  • Nyx PDF Classifier malicious score 1.0000

Heuristics 9

  • PDF JavaScript exploit cluster critical PDF_JS_EXPLOIT_CLUSTER
    PDF combines an executable JavaScript/action surface with exploit staging indicators such as eval/unescape/fromCharCode, XFA script content, or a related CVE pattern. Benign form JavaScript remains low-severity, but this correlated cluster is high-confidence malicious behavior.
  • RichMedia (Flash) high PDF_RICHMEDIA
    PDF contains /RichMedia (Adobe Flash) which is a historic exploit vector
  • ASCIIHexDecode filter (with exploit indicators) medium PDF_FILTER_HEX
    Hex-encoding filter present alongside exploit delivery indicators — often used to hide payload or shellcode bytes
  • 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.
  • Embedded file low PDF_EMBEDDED
    PDF embeds a file attachment — could carry an executable or another weaponised document as a nested payload
  • 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)
  • Suspicious extracted artifact info 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.
  • 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.flashandmath.com
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#
    • http://ns.adobe.com/xap/1.0/
    • http://purl.org/dc/elements/1.1/
    • http://ns.adobe.com/xap/1.0/mm/
    • http://ns.adobe.com/xap/1.0/sType/ResourceRef#
    • http://adobe.com/AS3/2006/builtin

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
Adobe.swf
ce5f7936cf8e3536a88a804ce2d6902022df1794fa878bdc64a26866e34ba989		 pdf-embedded-file PDF EmbeddedFile object 16 at offset 0xAD1 55839 bytes
javascript_obj0006_000.js
80cfc1e9f47f7387c46d905c23a8b77fc1c047f1706a78596a6b02ee3ccad7d9		 pdf-javascript-stream PDF /JS object 6 at offset 0xF5 1576 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 2 eval/decoder/string-building token(s).

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