Malicious PDF — malware analysis report

Static analysis result for SHA-256 131cb981d5b15be9…

MALICIOUS

PDF

237.9 KB Created: 2009-06-06 21:05:54 +08:00 Authoring application: Acrobat Distiller 7.0 (Windows)
MD5: 9ff0b3c1ebea3f3608d74eaaeaa09ae1 SHA-1: 06350798a1c5f7e7496f2e011ef874611763552b SHA-256: 131cb981d5b15be9153ed8fcdd7188659c8be34bc235ae5913c75f0f27536610
152 Risk Score

Malware Insights

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

The PDF file contains embedded JavaScript that is heavily obfuscated and utilizes unescape functions, indicating malicious intent. The ML classifier and heuristic firings strongly suggest this is an exploit attempting to execute code. The primary function of the script appears to be downloading and executing a second-stage payload, though the exact URL is not directly visible due to obfuscation.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9998

Heuristics 7

  • 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.
  • unescape() call high PDF_UNESCAPE
    unescape() found — often used to decode shellcode in PDF JS exploits (matched inside decoded stream)
  • 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.
  • Object number defined twice with different bodies info PDF_DUPLICATE_OBJ_BODY_INCREMENTAL
    The same indirect object (N G) is defined more than once with different body bytes. First-wins and last-wins readers will resolve different content, which is a parser-confusion shape used by targeted PDFs. Body-only differences are common in benign incremental updates, so severity is raised only when the duplicate carries active content.
  • 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.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/xap/1.0/
    • http://ns.adobe.com/xap/1.0/mm/
    • http://purl.org/dc/elements/1.1/

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0022_000.js
0aaad551850424ba802fd4bd6dbfdadf6e6d74091c1e34d81f286071bfeb4e44		 pdf-javascript-stream PDF /JS object 22 at offset 0x3A085 6046 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 22 eval/decoder/string-building token(s).

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