PDF malware analysis — malicious · a08a78646f8dd964

MALICIOUS

PDF

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

MD5: a36821ca9d86790778bdf65b96a3ef18 SHA-1: 06ef7ff491771586b4163d16ca298356c7b9baa4 SHA-256: a08a78646f8dd964ea8427c8818b878d937fe37b43315b28fe55d6bff81a16dd

96 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Phishing: Spearphishing Attachment T1027 Obfuscated Files or Information

The PDF file contains embedded JavaScript, identified by the 'PDF_JAVASCRIPT' and 'PDF_JS' heuristics. The 'PDF_METADATA_EVAL_STAGER' heuristic indicates that this JavaScript is used to decode and execute a payload, likely leveraging 'String.fromCharCode' as seen in the document body and script content. The ML classifier strongly suggests malicious intent. The primary attack pattern involves obfuscated JavaScript within the PDF metadata to initiate a malicious execution chain.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 4

PDF metadata JavaScript eval stager high PDF_METADATA_EVAL_STAGER

PDF JavaScript reads document metadata fields such as title, subject, or producer, decodes character data with parseInt/String.fromCharCode style helpers, and evals the recovered stage. This is a high-signal exploit-kit staging pattern.
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` `b01f2b134db9a008623bb140bcac84250b2f289191b5afbf90dced7a9e4e596d`	pdf-javascript-stream	PDF /JS object 1 at offset 0x617D	460 bytes

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