怎么样防止针对织梦DEDECMS网站的DDos攻击?

if($cfg_anquan_cc == 'Y'){//php防CC攻击 在3秒内连续刷新页面5次以上将指向本机 http://dede58.com/404.htm$P_S_T = $t_array[0] + $t_array[1];$timest amp = time();session_start();$ll_nowtime = $timestamp ;if (session_is_registered('ll_lasttime')){$ll_lasttime = $_SESSION['ll_lasttime'];$ll_times = $_SESSION['ll_times'] + 1;$_SESSION['ll_times'] = $ll_times;}else{$ll_lasttime = $ll_nowtime;$ll_times = 1;$_SESSION['ll_times'] = $ll_times;$_SESSION['ll_lasttime'] = $ll_lasttime;}if (($ll_nowtime - $ll_lasttime)<3){if ($ll_times>=5){header(sprintf("Location: %s",'http://www.copyie.com/404.htm'));exit;}}else{$ll_times = 0;$_SESSION['ll_lasttime'] = $ll_nowtime;$_SESSION['ll_times'] = $ll_times;}}