6. (30 points) Internet Censorship and Circumvention. The Great Firewall of China is a set of...

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6. (30 points) Internet Censorship and Circumvention. The Great Firewall of China is a set of technologies that mainland China uses to block access to parts of the internet to their citizens. Monitoring systems are placed at gateways connecting internal traffic to the rest of the internet. These monitoring systems then examine traffic and block or censor unwanted connections. (a) One method that can be used to block traffic is using the DNS protocol. Briefly describe how the Great Firewall of China could build a system to block access to selected hosts on the internet using DNS, while letting all other traffic through. (b) How could someone in China circumvent your DNS-based blocking system to get to a host on the internet? (c) Describe one way that the Great Firewall could block your circumvention attempt in part (b). 2 (d) Another method that the Great Firewall uses to block traffic is using TCP resets. Assuming that the firewall can monitor all traffic that passes through the gateway, describe how it could block traffic using a TCP reset. 6. (30 points) Internet Censorship and Circumvention. The Great Firewall of China is a set of technologies that mainland China uses to block access to parts of the internet to their citizens. Monitoring systems are placed at gateways connecting internal traffic to the rest of the internet. These monitoring systems then examine traffic and block or censor unwanted connections. (a) One method that can be used to block traffic is using the DNS protocol. Briefly describe how the Great Firewall of China could build a system to block access to selected hosts on the internet using DNS, while letting all other traffic through. (b) How could someone in China circumvent your DNS-based blocking system to get to a host on the internet? (c) Describe one way that the Great Firewall could block your circumvention attempt in part (b). 2 (d) Another method that the Great Firewall uses to block traffic is using TCP resets. Assuming that the firewall can monitor all traffic that passes through the gateway, describe how it could block traffic using a TCP reset.