PDF malware analysis — malicious · c42b1b461001b509

MALICIOUS

PDF

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

MD5: afaa85b1873d1ab36a03c02ec320a946 SHA-1: 6a6b4127dd8ba5d37ff956543141e8424383af60 SHA-256: c42b1b461001b509186299e983a84c1a72575ab1a85b182671154dc5b1222019

94 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The PDF file contains embedded JavaScript, identified by heuristics like 'PDF_JAVASCRIPT' and 'PDF_JS'. The 'PDF_METADATA_EVAL_STAGER' heuristic indicates that the JavaScript is used to decode and execute further code, likely from the embedded 'javascript_obj0001.js' stream. The ML classifier strongly flags this PDF as malicious. The presence of String.fromCharCode further suggests obfuscation techniques common in malicious PDFs. The primary attack pattern involves leveraging PDF's JavaScript capabilities to initiate a malicious execution chain.

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` `f5d3e04c5639c94b5ad1edab62d85408c1f43b45311f2dc01e6b82d281137108`	pdf-javascript-stream	PDF /JS object 1 at offset 0x6315	524 bytes

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