PDF malware analysis — malicious · 81b7774c3a73868f

MALICIOUS

PDF

26.0 KB Created: 2011-72-51 03:25:00 Authoring application: String.fromCharCode

MD5: 1a21837c71232569e629db73a14bf678 SHA-1: c053074206010115758d029e507636511acd73da SHA-256: 81b7774c3a73868f8c31fca097045c0b2e22018b2fea25214b3d7a99b5a1d5ee

96 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1059.007 JavaScript

This PDF sample contains embedded JavaScript, flagged by multiple heuristics including PDF_JAVASCRIPT, PDF_JS, and PDF_EVAL. The ML classifier strongly indicates maliciousness. The JavaScript stream, named 'javascript_obj0001_000.js', is likely responsible for downloading and executing a second-stage payload, as suggested by the use of eval() and string concatenation techniques within the script. The 'String.fromCharCode' usage in the document body and metadata further supports obfuscation.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 5

eval() call high PDF_EVAL

eval() found — commonly used for obfuscated exploit execution (matched inside decoded stream)
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.
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 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0001_000.js` `504f90d1051fcf171549d34e126d2791d18b22cc9f68127e15adf607b4458b71`	pdf-javascript-stream	PDF /JS object 1 at offset 0xA	907 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 5 eval/decoder/string-building token(s).

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