PDF malware analysis — malicious · 728a305c106babba

MALICIOUS

PDF

118.6 KB

MD5: f4b228d7f4ade5b5802fe03aa39b5d65 SHA-1: a9a1fceaa1116a5e8d714e134332aab40395e5df SHA-256: 728a305c106babba0c84da330b25799c9f46446c1d048c4e14540bedffc3bea2

256 Risk Score

Malware Insights

MITRE ATT&CK

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

The sample is a PDF file that contains embedded JavaScript, as indicated by multiple PDF-specific heuristics including 'PDF_JAVASCRIPT', 'PDF_JS', and 'PDF_JS_EXPLOIT_CLUSTER'. The JavaScript stream utilizes 'eval()' and 'String.fromCharCode()', common techniques for obfuscation and execution of malicious code. The 'ML_NYX_PDF_MALICIOUS' and 'CLAMAV_DETECTION' heuristics further confirm its malicious nature, with ClamAV identifying it as 'Pdf.Exploit.Agent-36086'. The primary function of the JavaScript appears to be downloading and executing a secondary payload, a common tactic for PDF-based exploits.

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 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0006_000.js` `597537b07071792e05c3c6fd083a3e9d927cb4fe1c558645bfdabcb0a267c7e5`	pdf-javascript-stream	PDF /JS object 6 at offset 0x143	627659 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).

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