PDF malware analysis — malicious · fc355a3427a5a475

MALICIOUS

PDF

19.7 KB

MD5: cb5759bc0b712120c14c5bdb47416580 SHA-1: 83c405ef4410d9fbed13f0c418142eb606f7134d SHA-256: fc355a3427a5a475980dc46a1d76458bc92529e7c8bc4bb9024000f52779bc7d

64 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The PDF contains embedded JavaScript, indicated by multiple heuristic firings including PDF_JAVASCRIPT and PDF_JS. The ML classifier strongly flagged this PDF as malicious. The embedded JavaScript, particularly the deobfuscated 'numeric_charcode_stage_000.js', uses String.fromCharCode to reconstruct and execute code, a common technique for obfuscating malicious payloads. This script likely downloads and executes a second-stage payload, aligning with the overall malicious verdict.

Machine Learning

Nyx PDF Classifier malicious score 0.9998

Heuristics 5

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)
syncAnnotScan annotation-staging primitive low PDF_FOXIT_SYNCANNOTSCAN

PDF JavaScript calls syncAnnotScan() — a no-op annotation-enumeration primitive used by exploit-kit JavaScript to stage payload reads from annotation /Subject fields before eval(). Not a vulnerable sink itself; rarely seen in legitimate PDFs. (identified after JavaScript deobfuscation)
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_obj0004_000.js` `b771a67801a2a024471cb29d8ce119b13dc98b5c56ef213dece7e1a5cc7b8bed`	pdf-javascript-stream	PDF /JS object 4 at offset 0xE1	1814 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`numeric_charcode_stage_000.js` `4718a27c2224fc36bf24f8e8e04598f1ad78adce4401c7be2708318738a6983d`	deobfuscated-js	numeric char-code string decoded JavaScript at offset 0xEF	469 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).

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