PDF malware analysis — malicious · 9bac5d9db34c8cb1

MALICIOUS

PDF

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

MD5: 997946ae577ce503c4ac7554e97c6a61 SHA-1: 20abff58562717114df0cf75f5b9cfb45bfb322a SHA-256: 9bac5d9db34c8cb1f0513d3cd16333772f34ac2348dbbd8836a9b35da9074e63

94 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The PDF file contains embedded JavaScript, identified by heuristics such as 'PDF_JAVASCRIPT' and 'PDF_JS'. A high-confidence heuristic 'PDF_METADATA_EVAL_STAGER' indicates that the JavaScript is used as a stager within the PDF metadata to decode and execute further code. The 'ML_NYX_PDF_MALICIOUS' classifier strongly supports a malicious verdict. The presence of 'String.fromCharCode' in the document body and metadata suggests obfuscation techniques commonly used to hide malicious JavaScript, which likely acts as a downloader for a second-stage payload.

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` `a06ca6024a0b1d65b2bddff831ee9c8dd1f1e2af056f14577db8347822fb4dc7`	pdf-javascript-stream	PDF /JS object 1 at offset 0x6175	536 bytes

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