PDF malware analysis — malicious · 64373156f4951076

MALICIOUS

PDF

18.0 KB Created: 2011-72-51 03:25:00 Authoring application: String.fromCharCode

MD5: b83885378279017f3e1a7d0740121f49 SHA-1: 683c4740df3dae656ab603e359ebc9b8a579cd89 SHA-256: 64373156f4951076ab8c19c9fafda3ea0a2b29ee3682c7e9595ebf237852d0d3

114 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 utilizes String.fromCharCode and obfuscation techniques to construct and execute a payload. The script appears to download and execute a second-stage payload, indicated by the critical heuristic PDF_JS_EXPLOIT_CLUSTER and the ML classifier's high confidence. The use of JavaScript within a PDF points to T1059.007, and the overall execution of a payload suggests T1203. Given the nature of PDF exploits, T1566.001 is also relevant as a likely initial access vector.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 4

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.
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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0001_000.js` `15ee9f1141374e4f54ff87552307a82beca396b1992bc5d41927f9fdf4254d8a`	pdf-javascript-stream	PDF /JS object 1 at offset 0x45B9	339 bytes

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