PDF malware analysis — malicious · 1ef1932a5c2c12e9

MALICIOUS

PDF

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

MD5: 9de5cfcd3927855ce7df03f6d23f0fcb SHA-1: d39910d9736a7c1b55ea397b782ae79ead708ceb SHA-256: 1ef1932a5c2c12e9e0343a7865ea0189e3a9ab007eed5015cc3e258e8c1e86e5

94 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The PDF file contains embedded JavaScript, specifically utilizing String.fromCharCode and an eval stager within its metadata. This JavaScript is designed to decode and execute arbitrary code, a common technique for downloading and running secondary payloads. The ML classifier strongly indicates maliciousness, and the heuristics point to a stager mechanism.

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` `db99512bbd9e7f59bb6c7aee89fc442f515a0863a26f921abe3359579e6fe486`	pdf-javascript-stream	PDF /JS object 1 at offset 0x62BB	514 bytes

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