PDF malware analysis — malicious · 9facf3b5110ee963

MALICIOUS

PDF

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

MD5: 02438937bada6ae36e2a1ed559509e6c SHA-1: fc46e0c28474370d947d731c52da47afe8825b2f SHA-256: 9facf3b5110ee9636ca948303cb83b500c183028f9717950c6c77ff1a84bc42c

94 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

This PDF file was flagged as malicious by an ML classifier and contains JavaScript embedded within its metadata. The JavaScript uses String.fromCharCode, a common technique for obfuscation, and is likely acting as a stager to download and execute a secondary payload. The presence of PDF_METADATA_EVAL_STAGER heuristic further supports this assessment.

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` `b609e51ea20c58ba7b87df2537c31597121c812b21ff7041210623c5173a7718`	pdf-javascript-stream	PDF /JS object 1 at offset 0x6303	530 bytes

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