PDF malware analysis — malicious · 163fa0701bc7385e

MALICIOUS

PDF

118.7 KB

MD5: f40586e2bd813bc0433277b67f6695b8 SHA-1: f8f138058d08361d5e5968fc5b11367295be2257 SHA-256: 163fa0701bc7385e5b93fc7b5e1adf5c01e096d03503de476120534dd0e0600b

256 Risk Score

Malware Insights

MITRE ATT&CK

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

The PDF file contains heavily obfuscated JavaScript, indicated by multiple heuristic firings including 'PDF_EVAL', 'PDF_FROMCHARCODE', and 'PDF_JS_LARGE_COMMENT_PADDED_EVAL'. The ClamAV detection 'Pdf.Exploit.Agent-36086' and the ML classifier strongly suggest malicious intent. The JavaScript's primary function appears to be downloading and executing a secondary payload, a common technique for initial access via spearphishing attachments.

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` `4674c8fc85a4957c6d44ecdfb147a2118abf22260a62b22efc7cdc1516789786`	pdf-javascript-stream	PDF /JS object 6 at offset 0x143	627619 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` `dff2bdfdb763f8f9572293aa16745433f4da2ffccff1d23b36a6a37490638f42`	deobfuscated-js	double percent-decoded annotation JavaScript at offset 0x143	262116 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 588 long base64-like blob(s).

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