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Computer Networking Security - Assignment Example

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The vulnerabilities created by the IP table rules above are that; an intruder can access the company resources through connection from the Internet to the router host machine ( links the Intranet to the subnet server) that is connected to the Internet or through the VPN. The…
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Computer Networking Security
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Computer Networking Security Part I. Firewall Rules Network Firewall rules #!/bin/sh # flushing all the existing filter table rules
/sbin/iptables -t filter -F INPUT
/sbin/ipchains -F
# no traffic to server subnet 140.192.39.0/24 on TCP and UDP
/sbin/iptables -A INPUT -p tcp -m multiport --dports 9000,4001:6999 -d 140.192.39.0/24 -j DROP
iptables -A INPUT -p tcp -m multiport –dports 1025:4000,7000:9000 -s 140.192.39.0/24 -j ACCEPT
#no traffic for port 9000, 40001:6999 but allow below 4000 and between 7000:9000 from 140.192.39.0/24
/sbiniptables -A INPUT -p udp -m multiport --destinatio-ports 9000,4001:6999 -d 140.192.39.0/24 -j DROP
/sbiniptables -A INPUT -p udp -m multiport --dports 1025:4000,7000:9000 -s 140.192.39.0/24 -j ACCEPT
#allowing inbound Internet traffic to VPN on port 1723 (set VPN host IP address 140.192.39.5 )
iptables -A INPUT -p tcp –dport 1723 -d 140.192.39.5 -j ACCEPT
iptables -A INPUT -p udp –dport 1723 -d 140.192.39.5 -j ACCEPT
#blocking VPN traffic from E, M, S on subnet server
iptables -A INPUT -p tcp -s 168.192.2.0/24 –dport 1723 -d 140.192.39.0/24 -j DROP
/sbin/iptables -A INPUT -p tcp -s 168.192.3.0/24 --dport -d 1723 -d 140.192.39.0/24 -j DROP
/sbin/iptables -A INPUT -p tcp -s 168.192.4.0/22 –dport -d 140.192.39.0/24 -j DROP
#no traffic from M and S to application server on port range 3000 to 4000
M - iptables -A INPUT -p tcp -s 168.192.3.0/24 -m multiport --dport 3000:4000 -d 140.192.39.0/24 -j DROP
S - iptables -A INPUT -p tcp -s 168.192.4.0/22 -m multiport --destination-port 3000:4000 -d 140.192.39.0/24 -j DROP
#all traffic to port range 3000:4000 on application server must come from E
iptables -A INPUT -p tcp -s 168.192.2.0/24 -m multiport --dport 3000:4000 -d 140.192.39.0/24 -j ACCEPT
#accept traffic to application server running SQL server (set SQL application server host IP address as 140.192.39.10 ) on tcp port 1433
/sbin/iptables -A INPUT -p tcp –dport 1433 -d 140.192.39.10 -j ACCEPT
#deny general service traffic to application servers
iptables -A INPUT -p tcp -m multiport –dport 1:1024 -d 140.192.39.0/24 -j DENY
#permit traffic to application server on ports above 1024 except between 3000 to 4000
iptables -A INPUT -p tcp -m multiport –dport 1025:2999 -d 140.192.39.0/24 -j ACCEPT
iptables -A INPUT -p udp -m multiport –dport 1025:2999 -d 140.192.39.0/24 -j ACCEPT
iptables -A INPUT -p tcp -m multiport –dport 4001:65535 -d 140.192.39.0/24 -j ACCEPT
iptables -A INPUT -p udp -m multiport –dport 4001:65535 -d 140.192.39.0/24 -j ACCEPT
Application server Firewalls Rules
#SQL server rules (set SQL application server host IP address as 140.192.39.10 )
iptables -A INPUT -p tcp –dport 1433 -d 140.192.39.10 -j ACCEPT
iptables -A INPUT -p tcp –sport 1433 -s 140.192.39.10 -j ACCEPT
#Application server 1 in server subnet (set IP address 140.192.39.11 )
/sbiniptables -A INPUT -p tcp –m multiport --dport 1:1024 -d 140.192.39.11 -j DENY
sbin/iiptables -A INPUT -p tcp –m multiport --dport 1025:2999,4001:65535 -d 140.192.39.11 -j ACCEPT
#Application server 2 in server subnet (set IP address 140.192.39.12 )
iptables -A INPUT -p tcp –m multiport --dport 1:1024 -d 140.192.39.12 -j DENY
iptables -A INPUT -p tcp -s 168.192.2.0/24 –m multiport --dport 3000:4000 -d 140.192.39.12 -j ACCEPT
sbin/iiptables -A INPUT -p tcp –m multiport --dport 1025:2999,4001:65535 -d 140.192.39.12 -j ACCEPT
iptables -A INPUT -p tcp -s 140.192.39.12 –m multiport --dport 1:4000,7000-9000 -d 168.192.4.0/22 -j ACCEPT
#Application server 3 in server subnet (set IP address 140.192.39.13 )
iptables -A INPUT -p tcp -s 140.192.39.13 –m multiport --dport 1:4000,7000-9000 -d 168.192.3.0/24 -j ACCEPT
iptables -A INPUT -p tcp -s 168.192.3.0/24 –m multiport --dport 3000:4000 -d 140.192.39.13 -j DENY
iptables -A INPUT -p tcp -s 168.192.4.0/22 –m multiport --dport 3000:4000 -d 140.192.39.13 -j DENY
#log all VPN traffic on each server
/sbin/iptables -A OUTPUT -m limit --limit 12/hour -j LOG --log-level 4 --log-prefix VPN traffic log
Part II. Firewall Problems
The vulnerabilities created by the IP table rules above are that; an intruder can access the company resources through connection from the Internet to the router host machine ( links the Intranet to the subnet server) that is connected to the Internet or through the VPN. The VPN created does not limit devices connected to it access other application servers over the Internet.
An executive cannot log into the application servers in the company from a home network because he will need Internet for the connection to be complete. It means that he has to use the VPN created in order to access the company resources. VPN only uses TCP port 1723 while the executive Intranet cannot access the application servers through this port. The connection will, therefore, be blocked as it will be malicious.
The assistant administrator cannot log into the application server through ssh since it requires him to use port 22 which is a port below 1024. All ports below the range of 1024 have been restricted for general purpose use.
Part III. Firewall Specifications Redesign
The vulnerabilities created can be solved by giving specific port addresses access to the application servers instead of allowing a certain range. Some Internet traffic to the VPN should be limited instead of allowing all inbound traffic to be accepted.
The executive can be given access to the application servers he uses from his home network by implementing a rule that allows subnet E traffic to be sent through VPN port 1723.
Assistant network administrator can be given access rights to the application server through providing specific access rules for him by specifying his mac address as an exception and opening some general purpose ports for him.
Additional IP table rules can include rules that restrict the number of parallel connections from one IP client. The network administrator should also implement an IP table rule that only opens a particular range of IP addresses in regards to IP addresses of the several subnets created. The administrator can also provide a strong way of authenticating users to the company network or the VPN and strong encryption methods of for the VPN.
Reference List
Eric Seargren, (2011). Secure Your Network for Free. Elsevier. New York. Read More
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