What are alternatives to secure a web-server other than firewall
<p>I'm doing a network security course and trying to wrap my head around all the concepts. One of which is: </p>

<p><strong>What technology other than firewall can be used to allow only a specific customers while block some other customers? Why is firewall not suitable?</strong> </p>

<p>During the course, I've been learning about all the security tools such as: <em>firewall (static, dynamic, DPI), Proxy, VPN, Tunnel, all sorts of IDS (signature, anomaly, darknet/greynet and honeypot) then mod_security</em> to secure apache but still puzzled by this question. </p>

<p>Any insights here will be greatly appreciated. </p>