Question requires you to develop firewall rules based on a fictitious organisation.
Scenario:
You work for a security-conscious company, xC-Cure, who develop encryption technologies for large corporate and defence customers world-wide. Your role is a junior security specialist and you have recently been asked to plan for the deployment of a new firewall.
The firewall is structured around an external filtering router (using NAT)with three(3) interfaces. The external (public) interface is Internet facing and has a public IP of 120.9.20.1. The second interface has an IP of 10.1.0.1 and is the gateway to the DMZ network (10.1.0.0). The third interface has an IP of 10.2.0.1 and is the gateway to the intranet (10.2.0.0). The firewall also acts as a VPN tunnel server on its public Internet interface.
While certain traffic can flow between the DMZ and the intranet, Internet initiated connections should not enter the intranet. Two sets of filtering rules are applied: one for traffic flowing in and out of the Internet interface, another for traffic flowing between the DMZ and the intranet.
The DMZ contains the following servers:
- A publicSecure Web Server (10.1.0.101) that accepts incoming https connections and makes connections to the Oracle Database inside the Intranet
- The Mail server (10.1.0.102) that accepts POP3 connections from the intranet and initiates and accepts SMTP connections to the Internet
The Intranet contains the following servers:
- The Oracle Database Server (10.2.0.10) that accepts SQLNet traffic from the Web Server in the DMZ
- The Intranet Web Server (10.2.0.11) that accepts HTTP traffic ONLY from within the intranet
- A File Share Server (10.2.0.12) that accepts SMBtraffic ONLY from with the intranet
Your rules should ensure that Internet access will be restricted to the following:
Only the following services will be permitted as OUTBOUND traffic (to the Internet from the DMZ or intranet):
- HTTPS and HTTP (from the intranet). Note: it is assumed that external Web access provides the ability to connect to the local Secure Web Server - no additional firewall rules are required.
- SMTP (from the Mail Server)
Only the following services will be permitted as INBOUND traffic (to the DMZfrom the Internet):
- HTTPS (to the Secure Web Server)
- SMTP (to the Mail Server)
Access between the Intranet and the DMZ will be restricted to the following. Only the following services will be permitted as OUTBOUND traffic (to the DMZ from the intranet):
- POP3 (from the intranet to the Mail Server)
- SSH (from the system administrators' subnet (10.2.5.0) to all DMZ servers)
Only the following services will be permitted as INBOUND traffic (from the DMZ to the intranet) traffic:
- Oracle (from the Secure Web Server)
The firewall is not to be accessible remotely on any interface - i.e. it should not accept connections on any of its IP addresses EXCEPT on its VPN port on the external interface.