PDF malware analysis — malicious · 187ad3fa5b213a17

MALICIOUS

PDF

118.5 KB

MD5: 5c68b5699b302cebf7b256fbf2da3513 SHA-1: 3959556a139c19c134cbc6a313490b509559ec37 SHA-256: 187ad3fa5b213a1731fc8d7c93356c86be77b8667bb5ee7f172c34c26e93edd4

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. Heuristics confirm this is a JavaScript exploit cluster, likely a stager designed to download and execute a second-stage payload. The ClamAV detection 'Pdf.Exploit.Agent-36086' further supports its malicious nature.

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` `177365b5c98e2b5b5c682201846ffe1dc7e8b9cde3a9ac13034da5378d370ba1`	pdf-javascript-stream	PDF /JS object 6 at offset 0x143	626639 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` `56d4a0a0af136410875261328f0c9d190798fb2eabfa3b00023d93759fbf9d30`	deobfuscated-js	double percent-decoded annotation JavaScript at offset 0x143	262144 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 621 long base64-like blob(s).

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