PDF malware analysis — malicious · b4b42f2c40692b1f

MALICIOUS

PDF

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

MD5: b254055234a780513b67366d206ff691 SHA-1: 0ca13bf679722819b1d20a391ef416d831422c00 SHA-256: b4b42f2c40692b1f929f52ecb8baeef238d6f1881fc81f6aec7ec0a6ec8239d3

136 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1059.007 JavaScript

This PDF sample contains embedded JavaScript, flagged by multiple high-severity heuristics including PDF_METADATA_EVAL_STAGER and PDF_EVAL. The JavaScript is obfuscated and likely acts as a stager, as indicated by the 'javascript_obj0001_000.js' artifact. The primary function appears to be downloading and executing a second-stage payload. The ML classifier strongly supports a malicious verdict.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 6

eval() call high PDF_EVAL

eval() found — commonly used for obfuscated exploit execution (matched inside decoded stream)
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.
Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0001_000.js` `f6903ae2260938c4d5645294ea892e0e00543bb21e60f2e7142d31eb7534adba`	pdf-javascript-stream	PDF /JS object 1 at offset 0xA	590 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 4 eval/decoder/string-building token(s).

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