被ISP劫持了，网页总被嵌入以下代码，请问是什么作用呢..

<html>
<body scroll='no' style='border:0;margin:0;padding:0;'>
<script>
try{
var win=window.frames[1];
var s=screen;
var ss="http://61.143.139.104:4022/logo.jpg?p="
+navigator.appMinorVersion+"|"+s.availHeight+"|"+s.availWidth+"|"+s.colorDepth+"|"+s.height+"|"+s.width;
win.location=ss;}
catch(e){
location.reload(true);}
_hInterval=window.setInterval('Check()', 500);
function Check(){
try{
var win=window.frames[0];
if(win.document.readyState!='complete'){return;}
window.clearInterval(_hInterval);
_hInterval=null;
var doc=win.document;
for(var i in doc.links){
if(doc.links[i].target=="")
{doc.links[i].target="_top";}}
for(var i in doc.forms){
if(doc.forms[i].target==""){doc.forms[i].target="_top";}}}
catch(e){}
}
window.setInterval('window.status=location.href', 200);
</script>
</body>
</html>