PDF malware analysis — malicious · 513f4ec5f0baa768

MALICIOUS

PDF

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

MD5: a66a2879ca1a1c0e0de60c08518bff18 SHA-1: ac4cf9cdea2f255d41f76cebd348664efba0915e SHA-256: 513f4ec5f0baa7684f3dc57d16f4e0e7e1bfda08facef16ea5fe44da522b7ddf

94 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The PDF file contains embedded JavaScript, indicated by multiple heuristic firings including 'PDF_JAVASCRIPT', 'PDF_JS', and 'PDF_METADATA_EVAL_STAGER'. The 'String.fromCharCode' function is used, suggesting obfuscation of JavaScript code. The ML classifier strongly flags this PDF as malicious. The primary attack pattern involves leveraging JavaScript within the PDF structure to execute arbitrary code, likely to download and execute a secondary payload. The confidence is slightly reduced due to the lack of specific IOCs beyond the obfuscation technique itself.

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` `d902866753bc6e86b92265917f32e41d61b5dc71186e08a408966e4747f62eff`	pdf-javascript-stream	PDF /JS object 1 at offset 0x627C	513 bytes

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