PDF malware analysis — malicious · 551922a3fe80af1a

MALICIOUS

PDF

118.5 KB

MD5: e9d18a14d950ac26b79e459fe1bf40c8 SHA-1: da8dcac595c82c1243653ef5aa3d141c9b70a4ff SHA-256: 551922a3fe80af1a4c91b6e2820178cb259d1aa600c8249ddd8aca7dec23f7ec

196 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The PDF contains obfuscated JavaScript, indicated by multiple heuristic firings including 'PDF_JAVASCRIPT', 'PDF_JS', 'PDF_EVAL', and 'PDF_JS_LARGE_COMMENT_PADDED_EVAL'. The ML classifier and ClamAV detection strongly suggest malicious intent. The embedded JavaScript streams, particularly 'legacy_pdfkit_stage_000.js', are likely responsible for downloading and executing a second-stage payload, as suggested by the 'ML_NYX_PDF_MALICIOUS' and 'CLAMAV_DETECTION' heuristics.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 7

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` `a471b7abd4cd30acc8f24dc74573eedd996129966f6c63033a96f9351e946c23`	pdf-javascript-stream	PDF /JS object 6 at offset 0x143	627185 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` `df66918dc984481f1844d4ce4d286a20577778a643882cd59652dfb701ef6948`	deobfuscated-js	double percent-decoded annotation JavaScript at offset 0x143	262118 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 688 long base64-like blob(s).

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