PDF malware analysis — malicious · 1bdf21f82467e8c8

MALICIOUS

PDF

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

MD5: aa6ebf26681d1740bffe4502d31a9536 SHA-1: 37803f1e0c9526f51c1dabd07f8ad1a9fbec94ab SHA-256: 1bdf21f82467e8c86cff1f18abc236d3ab4cb135eb23ab71d3b368f2ac59463f

94 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The PDF file contains embedded JavaScript, identified by heuristics like 'PDF_JAVASCRIPT' and 'PDF_JS'. The 'PDF_METADATA_EVAL_STAGER' heuristic indicates that JavaScript within the PDF's metadata is used to decode and execute code. The presence of 'String.fromCharCode' further suggests obfuscation techniques common in JavaScript payloads. The ML classifier strongly flags this PDF as malicious. The primary intent appears to be the execution of a stager that likely downloads and runs 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` `478fe9225989cf2ae29227b6f46a802a4f75e494eb9c969140cf013976004dd1`	pdf-javascript-stream	PDF /JS object 1 at offset 0x6255	459 bytes

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