[cycopia]

At the beginning of your index.php file in your admincp folder, add the following:

if(!preg_match("/^(68\.142\.18\.|68\.143\.19\.)/",$_SERVER['REMOTE_ADDR'])){
	header("HTTP/1.0 403 Forbidden",1);
	echo "<h2>403 Forbidden</h2>";
	exit();
}

The above code only allows ip addresses that begin with 68.142.18. or 68.143.19. Multiple IPs are separated by a | (pipe, above a back-slash on keyboard). You will notice that all periods are back-slash escaped (coding standard for regular expressions). Also be sure to not forget that last period after the 3rd number.

if(!preg_match("/^68\.142\.1\.143/",$_SERVER['REMOTE_ADDR'])){
	header("HTTP/1.0 403 Forbidden",1);
	echo "<h2>403 Forbidden</h2>";
	exit();
}

The above code allows only the IP 68.142.1.143.
Here is an example of the WRONG way:

if(!preg_match("/^68\.142\.1/",$_SERVER['REMOTE_ADDR'])){
	header("HTTP/1.0 403 Forbidden",1);
	echo "<h2>403 Forbidden</h2>";
	exit();
}

This code is missing a vital period after the 3rd number! We will allow any ip matching the pattern of 68.142.1*. That means 68.142.1.*, 68.142.10.*, 68.142.11.*, 68.142.12.*, 68.142.100.*, and so on all pass our "test." Don't forget the last period because you can go from letting a few ips to thousands by mistake.