If you’re planning on taking the Security+ exam, you should have a basic understanding of how you can protect Internet-facing servers. One way is with a network perimeter, but there are others.
For example, can you answer this question?
Q. Your organization hosts a web server and wants to increase its security. You need to separate all web-facing traffic from internal network traffic. Which of the following provides the BEST solution?
A. VLAN
B. Firewall
C. DMZ
D. WAF
More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation is available at the end of this post.
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Network with Demilitarized Zone
The demilitarized zone (DMZ) is a buffered zone between a private network and the Internet. Attackers seek out servers on the Internet, so any server placed directly on the Internet has the highest amount of risk. However, the DMZ provides a layer of protection for these Internet-facing servers.
As an example, the following figure shows a common network configuration with a DMZ. The DMZ is the area between the two firewalls (FW1 and FW2) and hosts several Internet-facing servers. Many DMZs have two firewalls creating a buffer zone between the Internet and the internal network, as shown in the figure, though other configurations are possible.
Network with DMZ
In this configuration, one firewall separates the DMZ from the Internet. The second firewall separates the DMZ from the internal network. Each firewall includes detailed rules designed to filter traffic and protect both the internal network and the public servers. One way of saying this is that the DMZ provides access to the services hosted in the DMZ, while segmenting access to the internal network.
For example, FW1 can have rules to allow traffic to the servers in the DMZ, but block unsolicited traffic to FW2. The mail server would send and receive email to other email servers on the Internet through port 25 of FW1, and also send and receive email to internal clients through port 25 on FW2. The web server hosts web pages to any Internet users through ports 80 and 443 on FW1, but FW2 blocks these ports. The CA server validates certificates for Internet clients by answering through FW1.
Notice in the previous figure that the intranet includes a database server. The web server may use this to create web pages for an e-commerce site. It could hold product data, customer data, and much more. FW2 allows traffic between the web server (and only the web server) and the database server on port 1433. FW2 would block all other Internet traffic to the database server.
The DMZ can host any Internet-facing server, not just those shown in the figure. Other examples include FTP servers used for uploading and downloading files and virtual private network (VPN) servers used for providing remote access.
Remember this
A DMZ is a buffer zone between the Internet and an internal network. It allows access to services while segmenting access to the internal network. In other words, Internet clients can access the services hosted on servers in the DMZ, but the DMZ provides a layer of protection for the internal network.
Q. Your organization hosts a web server and wants to increase its security. You need to separate all web-facing traffic from internal network traffic. Which of the following provides the BEST solution?
A. VLAN
B. Firewall
C. DMZ
D. WAF
Answer is C. A demilitarized zone (DMZ) is a buffered zone between a private network and the Internet, and it will separate the web server’s web-facing traffic from the internal network.
You can use a virtual local area network (VLAN) to group computers together based on job function or some other administrative need, but it is created on switches in the internal network.
A firewall does provide protection for the web server, but doesn’t necessarily separate the web-facing traffic from the internal network.
A web application firewall (WAF) protects a web server from incoming attacks, but it does not necessarily separate Internet and internal network traffic.
