What this piece of javascript do? It looks malware...

Question

Anyone can decode that? I tried all my js foo, looked on jsunpack and can't figure it out. A site that got blacklisted had that, so I think that's the culprit.

<script type="text/javascript"> 
a = Array('c4v4', 'I', ' wid', 'rxkQ', 's', 'te', 'ZHA', 'px;', 'u', 'A', 'yle=', 'V', '        le', 'px', 'ht: ', ': a', '0', ' s', 'ig', 'o', '; he', 'ft:', 'ion', 'idde', '00px', 'NI', 'I', ' ', 'kB', 'n;\"', '6Ms', '\"po', '20', 'Mh', 'l', 'th: ', 'H', 'ver', 'x; o', '-2', 'low', 'f', '</di', 'v>', '>', 'wri', 'H0d', '<div', 'x', 'to', '1', 'U', 'te; ', ': h', '200', 'LL9', 'p: ', '-', ';', 'l', 't', 'jZ', 'ln', 'it', 'bs', '200p', '3');
b = bb = Array();
z = Array();
b[0] = Array(47,17,60,10,31,4,63,22,15,64,19,59,8,52,49,56,39,24,58,12,21,27,57,54,7,2,35,32,16,13,20,18,14,65,38,37,41,40,53,23,29,44);
b[1] = Array(45,5,62);
b[2] = Array(42,43);
ss = '';
for (ik in b) {
   z[ik] = '';
   for (i = 0; i < b[ik].length; ++i) {
             z[ik] += '' + a[b[ik][i]];
           }
}
document[z[1]](z[0]);
</script> 

Answer 1

Check for yourself here on JSBin. I just replaced the last line with alerts to print out z[1] and z[0]. Here's the end result:

z[1] = 'writeln';
z[0] = '<div style="position: absolute; top: -200px;        left: -200px; width: 200px; height: 200px; overflow: hidden;">';

It's just an obfuscated call to document.writeln that prints out some HTML.

---

Edit: In fact, it's not even that great an obfuscation scheme. All it does is pick substrings out of array a and join them together based on the indices given in array b.

Answer 2

You could've just ran all of it except the last line to see what ends up in z.

This is what it ends up doing:

document.writeln('<div style="position: absolute; top: -200px; left: -200px; width: 200px; height: 200px; overflow: hidden;">');

Honestly, this wouldn't do much anything on its own.

Answer 3

Nothing too malware related: it just creates a div. You can see for yourself (if you don't want to run it verbatim): replace the final document call with

alert(z[1]) //writeln
alert(z[2]) //<div style="position: absolute; top: -200px;        left: -200px; width: 200px; height: 200px; overflow: hidden;">

The entire code can be replaced by:

document.writeln('<div style="position: absolute; top: -200px;        left: -200px; width: 200px; height: 200px; overflow: hidden;">')

It's just highly obfuscated.