PDF malware analysis — malicious · 0bbd0f4c143ab4c5

MALICIOUS

PDF

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

MD5: d7a883ba87ddeaa79266f8a012c22b9b SHA-1: 4c33ffe9c641b0803dca9abbd15539ce9d92345a SHA-256: 0bbd0f4c143ab4c5df22308292308f4bfc9297deeb28dbe25a96415b6a06aba1

114 Risk Score

Malware Insights

MITRE ATT&CK

T1059.007 JavaScript T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The PDF file contains embedded JavaScript that is obfuscated using String.fromCharCode and string manipulation. The script appears to download and execute a second-stage payload, indicated by the critical heuristic firing 'PDF_JS_EXPLOIT_CLUSTER' and the ML classifier's high confidence. The script's logic suggests it reconstructs a command or URL from manipulated document properties and then executes it.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 4

PDF JavaScript exploit cluster critical PDF_JS_EXPLOIT_CLUSTER

PDF combines an executable JavaScript/action surface with exploit staging indicators such as eval/unescape/fromCharCode, XFA script content, or a related CVE pattern. Benign form JavaScript remains low-severity, but this correlated cluster is high-confidence malicious behavior.
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` `815e37815fec07a7aa4ee2a598ae9ca3b08c1043543394706e191b9de2354e29`	pdf-javascript-stream	PDF /JS object 1 at offset 0x459F	328 bytes

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