Illustrate Screened subnet firewall Architecture.

Screened Subnet Firewall Architecture

A screened subnet firewall architecture (also known as a DMZ or demilitarized zone) is a robust network security configuration that adds an additional layer of security between the public internet and an organization's internal network. This architecture involves multiple firewalls and network segments to isolate and protect sensitive internal systems from external threats.

Components of Screened Subnet Firewall Architecture

1. External Firewall: Protects the DMZ and internal network from direct exposure to the internet.
2. DMZ (Demilitarized Zone): An isolated network segment that hosts public-facing services, such as web servers, email servers, and DNS servers. These services can be accessed from the internet but are isolated from the internal network.
3. Internal Firewall: Provides an additional layer of protection for the internal network, ensuring that even if the DMZ is compromised, the internal network remains secure.
4. Internal Network: The protected network segment where sensitive data and internal systems reside.

Architecture Diagram

              [Internet]
                  |
                  |
         [External Firewall]
                  |
                  |
                [DMZ]
         (Web Servers, Email Servers, etc.)
                  |
                  |
         [Internal Firewall]
                  |
                  |
         [Internal Network]
        (Database Servers, Internal Systems, etc.)

Detailed Explanation

1. External Firewall:

   • Role: Acts as the first line of defense against external threats. It filters incoming and outgoing traffic based on predefined security rules.
   • Configuration: Typically configured to allow traffic to and from the DMZ but restricts direct access to the internal network.
   • Rules:
     • Allow inbound traffic to public services in the DMZ (e.g., HTTP, HTTPS for web servers).
     • Block inbound traffic to the internal network.
     • Allow outbound traffic from the DMZ to the internet for necessary services (e.g., DNS queries).

2. DMZ (Demilitarized Zone):

   • Role: Hosts public-facing services that need to be accessible from the internet while isolating these services from the internal network.
   • Components: Web servers, email servers, DNS servers, and other public services.
   • Security: Even if a service in the DMZ is compromised, attackers cannot directly access the internal network due to the isolation provided by the internal firewall.

3. Internal Firewall:

   • Role: Provides an additional layer of security, protecting the internal network from any potential threats that might originate from the DMZ.
   • Configuration: Typically more restrictive, allowing only specific traffic from the DMZ to the internal network based on strict rules.
   • Rules:
     • Allow traffic from the DMZ to the internal network only if necessary (e.g., database queries from a web server to a database server).
     • Block all other traffic between the DMZ and the internal network.

4. Internal Network:

   • Role: The most protected network segment where sensitive data and critical internal systems are located.
   • Components: Database servers, internal application servers, user workstations, and other internal systems.
   • Security: Highly restricted access, with monitoring and logging to detect any unauthorized access attempts.

Advantages of Screened Subnet Firewall Architecture

1. Enhanced Security:

   • Multiple layers of defense make it more difficult for attackers to reach the internal network. Even if the DMZ is compromised, the internal firewall provides additional protection.

2. Isolation of Public Services:

   • Public-facing services are isolated in the DMZ, reducing the risk to the internal network. If a public service is compromised, the damage is contained within the DMZ.

3. Controlled Access:

   • Strict access control policies can be implemented, allowing only necessary traffic between network segments. This minimizes the attack surface.

4. Improved Monitoring:

   • Network traffic can be monitored and logged at multiple points (external firewall, DMZ, internal firewall), providing better visibility into potential threats and enabling quicker incident response.

Summary

The screened subnet firewall architecture is a robust and widely used network security configuration that provides enhanced protection for an organization's internal network by isolating public-facing services in a DMZ. By employing multiple firewalls and network segments, this architecture ensures that even if the DMZ is compromised, the internal network remains secure. This multi-layered approach to security helps in controlling access, improving monitoring, and mitigating the risk of attacks.

If you have further questions or need additional details on the screened subnet firewall architecture, feel free to ask!