PDF malware analysis — malicious · bf25cb0a970ff369

MALICIOUS

PDF

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

MD5: b21352a19854f99b47484db61ad2d8d7 SHA-1: 584945c1c61c671f19056f451c49b57022cbc9a1 SHA-256: bf25cb0a970ff369e86bc707197b082b1b4659b59841f7f067e9bbc0f7251025

94 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 Command and Scripting Interpreter: PowerShell

The PDF file contains embedded JavaScript, identified by heuristics like PDF_JAVASCRIPT and PDF_JS. The PDF_METADATA_EVAL_STAGER heuristic indicates that this JavaScript is used to decode and execute further code, a common technique for downloading and running second-stage malware. The ML classifier strongly flags this PDF as malicious. No specific family could be identified, but the attack pattern is consistent with a downloader.

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` `83bc571841c498f9d8247dec9260fbc8f919f87969cb38a91c0190ef4749123e`	pdf-javascript-stream	PDF /JS object 1 at offset 0x61A3	455 bytes

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