PDF malware analysis — malicious · 66bf7af397c855f9

MALICIOUS

PDF

12.1 KB

MD5: 1b9b6992489161dcb4877c526b0ba94c SHA-1: 52c8d451042dd08fd8056ba2a06bbac97d3b5303 SHA-256: 66bf7af397c855f90ee416274580f80dec9dcf87ac335ad72c777b9354ece3f6

116 Risk Score

Malware Insights

MITRE ATT&CK

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

The PDF file contains embedded JavaScript, identified by multiple heuristics including 'PDF_JAVASCRIPT' and 'PDF_JS_EXPLOIT_CLUSTER'. The JavaScript code, after being deobfuscated, uses String.fromCharCode and eval to construct and execute a payload. The script's primary function appears to be downloading and executing a second-stage payload from a remote source, indicated by the use of 'app.doc.getPageNumWords' and subsequent string manipulation. The ML classifier strongly indicates maliciousness.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 5

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.
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_obj0005_000.js` `f048286b2dfe205330e162117bc9e2e9406092389e25aa91660890d79cb205b6`	pdf-javascript-stream	PDF /JS object 5 at offset 0x107	916 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).

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