PDF malware analysis — malicious · 77d6b811fb3d9993

MALICIOUS

PDF

15.8 KB

MD5: cf6f7395f97e0ed43b36b6f99b014b6b SHA-1: 31db141a0059a21f11a5a258558f4f81a2ea4658 SHA-256: 77d6b811fb3d9993360df28f927a2a6b447f600624fa9453efd9a45bc8f2265d

256 Risk Score

Malware Insights

MITRE ATT&CK

T1059.007 JavaScript T1203 Exploitation for Client Execution

This PDF file contains embedded JavaScript that is heavily obfuscated and utilizes eval() and String.fromCharCode() functions, indicating an attempt to hide malicious code. The heuristics and ClamAV detection strongly suggest this is an exploit attempting to download and execute a secondary payload. The ML classifier also flagged this as highly malicious.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 8

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.
ClamAV: Pdf.Exploit.Agent-36086 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Pdf.Exploit.Agent-36086
eval() call high PDF_EVAL

eval() found — commonly used for obfuscated exploit execution (matched inside decoded stream)
Large comment-padded JavaScript eval stager high PDF_JS_LARGE_COMMENT_PADDED_EVAL

PDF JavaScript contains a very large stream padded with long random-looking block comments around String.fromCharCode and eval. This is an exploit-kit obfuscation shape used to bury a decoder and recovered stage inside noise, not normal PDF form automation.
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. (matched inside decoded stream)
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 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0006_000.js` `110860b8645629a0b2881245ba8e801f0a70ad913e8d4614e3c69ebf26a9e3dd`	pdf-javascript-stream	PDF /JS object 6 at offset 0x143	425393 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 eval/decoder/string-building token(s). Carved artifact contains 42 long base64-like blob(s).
`legacy_pdfkit_stage_000.js` `4bb0682a23fd4116767b1d8210e4b3beabf875028b041adecf5ca5c422e321a4`	deobfuscated-js	double percent-decoded annotation JavaScript at offset 0x143	262092 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 559 long base64-like blob(s).

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