Malware Insights
The PDF file contains embedded JavaScript, indicated by multiple heuristic firings including 'PDF_JAVASCRIPT' and 'PDF_JS'. The ML classifier strongly flagged this PDF as malicious. The embedded JavaScript, particularly the 'numeric_charcode_stage_000.js' file, appears to be obfuscated and uses 'String.fromCharCode' to reconstruct code, a common technique for evading static analysis and delivering a second-stage payload. The exact intent of the script is not fully discernible due to obfuscation, but its presence and the ML classification point to a malicious exploit.
Machine Learning
- Nyx PDF Classifier malicious score 0.9998
Heuristics 5
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JavaScript action low PDF_JAVASCRIPTPDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
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Embedded JS stream low PDF_JSPDF references a /JS stream. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
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String.fromCharCode low PDF_FROMCHARCODEString.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. (matched inside decoded stream)
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syncAnnotScan annotation-staging primitive low PDF_FOXIT_SYNCANNOTSCANPDF JavaScript calls syncAnnotScan() — a no-op annotation-enumeration primitive used by exploit-kit JavaScript to stage payload reads from annotation /Subject fields before eval(). Not a vulnerable sink itself; rarely seen in legitimate PDFs. (identified after JavaScript deobfuscation)
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Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGEOne 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 2
Files carved from inside the sample during analysis.
| Filename | Kind | Source | Size |
|---|---|---|---|
javascript_obj0004_000.jsb771a67801a2a024471cb29d8ce119b13dc98b5c56ef213dece7e1a5cc7b8bed |
pdf-javascript-stream | PDF /JS object 4 at offset 0xE1 | 1814 bytes |
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Detection
ClamAV:
No threats found
Obfuscation or payload:
likely
Carved artifact contains 1 eval/decoder/string-building token(s).
|
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numeric_charcode_stage_000.js4718a27c2224fc36bf24f8e8e04598f1ad78adce4401c7be2708318738a6983d |
deobfuscated-js | numeric char-code string decoded JavaScript at offset 0xEF | 469 bytes |
|
Detection
ClamAV:
No threats found
Obfuscation or payload:
likely
Carved artifact contains 1 eval/decoder/string-building token(s).
|
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