Full Answer Section

1. VPN Tunnel Establishment:
   • The remote site’s VPN router/firewall establishes a secure VPN tunnel with the organization’s Internet edge router.
   • This tunnel ensures encrypted communication over the public internet.  
2. Perimeter Defense (Firewall 1):
   • The encrypted VPN traffic arrives at the organization’s Internet edge router and is then routed to Firewall 1 (perimeter firewall).
   • Firewall 1 inspects the traffic based on defined rules (e.g., allowed VPN protocols, source IP addresses).  
   • Unauthorized traffic is blocked.
3. Proxy Server:
   • Traffic that is allowed by Firewall 1 is then sent to the proxy server.
   • The proxy server acts as an intermediary between the external network and the internal network.  
   • The proxy server can perform web filtering, content inspection, and caching.  
4. Intrusion Detection/Prevention System (IDS/IPS):
   • Traffic is then passed through an IDS/IPS.
   • The IDS monitors network traffic for suspicious patterns or anomalies.  
   • The IPS can actively block malicious traffic.  
   • This is where the data flow is monitored, as requested.
5. Internal Firewall (Firewall 2):
   • Firewall 2 further segments the network.
   • It controls traffic flow between the DMZ (where web servers reside) and the internal network.
   • This firewall limits access to sensitive internal resources.  
6. DMZ and Internal Network:
   • Web/application servers in the DMZ handle user requests.
   • Internal switches and firewalls provide further segmentation, protecting database servers and client devices.
   • Client devices are on their own segmented network.
7. Data Access:
   • The data from the remote user, if authorized, is then allowed to access the required data from the database servers.
   • The data is then sent back through the same route, in reverse, to the remote user.

CIA Triad and Layered Security

The CIA triad (Confidentiality, Integrity, Availability) is fundamental to information security. Layered security, as demonstrated in the network model, enhances each element:  

1. Confidentiality:
   • Ensures that data is accessible only to authorized individuals.
   • Layered Approach:
     • VPN encryption protects data in transit.  
     • Firewalls restrict access to sensitive network segments.  
     • Access control lists (ACLs) on switches and servers limit user privileges.  
     • Proxy servers can also prevent data leakage.  
     • Database encryption protects data at rest.  
2. Integrity:
   • Maintains the accuracy and completeness of data.
   • Layered Approach:
     • IDS/IPS detects and prevents unauthorized modifications.  
     • File integrity monitoring tools ensure data consistency.
     • Database transaction logs track changes.  
     • Hash functions can be used to verify file integrity.  
3. Availability:
   • Ensures that authorized users have timely and reliable access to information.
   • Layered Approach:
     • Redundant network devices and connections prevent single points of failure.  
     • Firewalls and IDS/IPS protect against denial-of-service (DoS) attacks.  
     • Load balancers distribute traffic across multiple servers.  
     • Backup and disaster recovery plans ensure data can be restored in case of an outage.  

Why Layered Security Helps:

• Redundancy: If one security layer fails, others provide protection.
• Defense in Depth: Multiple layers make it harder for attackers to penetrate the network.  
• Segmentation: Isolating network functions limits the impact of a breach.  
• Granular Control: Each layer can enforce specific security policies.

Credible Sources:

• NIST Cybersecurity Framework: Provides guidelines for implementing cybersecurity best practices.  
• SANS Institute: Offers resources on network security and defense in depth.
• OWASP (Open Web Application Security Project): Provides information on web application security.  
• Cisco and Juniper Networks: Network device manufacturers that provide documentation on firewall and VPN technologies.

By implementing a layered security approach, organizations can significantly improve their overall security posture and protect their valuable data.