PDF malware analysis — malicious · f7d000ff2d2be3d7

MALICIOUS

PDF

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

MD5: a04f4daec2b9977af8afc22c5b9f16fa SHA-1: f564fa8142029c4dfc4f77ef8f2310b3a1b774aa SHA-256: f7d000ff2d2be3d797bd136e15f3dee859995763b7e235c5fd02a1074e98c737

94 Risk Score

Malware Insights

MITRE ATT&CK

T1566.003 Phishing: Spearphishing via Service

The PDF file contains embedded JavaScript, flagged by multiple heuristics including 'PDF_JAVASCRIPT', 'PDF_JS', and 'PDF_METADATA_EVAL_STAGER'. The 'String.fromCharCode' function is used, indicating obfuscation to hide malicious JavaScript code within the PDF's metadata. This script is likely designed to download and execute a secondary payload, a common technique for initial access. The ML classifier strongly supports the malicious verdict.

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` `def0cf506f6a58766b8f0e446a9ea6d0956ef7e8ff33be08ce9a6be745adbcc7`	pdf-javascript-stream	PDF /JS object 1 at offset 0x62D4	540 bytes

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