CS6250 Module 10 Practice Exam 2026
Guide
1. What is DNS censorship? Large scale network traflc filtering strategy to
suppress material which they deem as objec-
tionable.
2. What are the properties of GFW (Great 1) Locality of GFW nodes - majority view is
Firewall of China)? that GFW censorship nodes are present at the
edge.
2) Centralized management - blocklists ob-
tained from two distinct GFW locations show
a high possibility of a central GFW manage-
ment entity that orchestrates blocklists.
3) Load balancing - GFW load balances be-
tween processes based on source and desti-
nation IP address.
3. Censorship Technique 1: DNS injection For DNS requests that are blocked by the
GFW, the GFW will respond with a fake DNS
record to prevent the client from reaching the
requested content.
4. 3 steps of DNS injection 1) DNS probe is sent to a DNS resolver
2) The probe is checked against the blocklist
3) A fake DNS A record response is sent back
if the request matches the blocklist. The direct
domain can be blocked, or specific domain
keywords can be blocked.
5. How many DNS Censorship Techniques 5
are there?
1/5
, CS6250 Module 10 Practice Exam 2026
Guide
6. 1. Packet dropping all network traflc going to a set of specific IP
addresses is discarded
Pros: (easy to implement, low cost)
Cons: (maintain a long blocklist, overblock-
ing)
7. 2. DNS Poisoning When a DNS receives a query for resolving
hostname to IP address - if there is no answer
returned or an incorrect answer is sent to
redirect or mislead the user request
Pros: (No overblocking)
Cons: (Blocks the entire domain)
8. 3. Content inspection all traflc traverses a proxy and is inspect-
ed for objectionable content, if matches ->
dropped
Pros: (precise censorship, flexible)
Cons: (not scalable)
9. 4. Blocking with reset sends a TCP (RST) to block individual connec-
tions that contain requests with objectionable
content.
10. 5. Immediate reset suspends traflc coming from a source imme-
diately, for a short period of time
11. What is overblocking? If two websites share the same IP address
and the intention is to only block one of them,
there's a risk of blocking both
12.
2/5
Guide
1. What is DNS censorship? Large scale network traflc filtering strategy to
suppress material which they deem as objec-
tionable.
2. What are the properties of GFW (Great 1) Locality of GFW nodes - majority view is
Firewall of China)? that GFW censorship nodes are present at the
edge.
2) Centralized management - blocklists ob-
tained from two distinct GFW locations show
a high possibility of a central GFW manage-
ment entity that orchestrates blocklists.
3) Load balancing - GFW load balances be-
tween processes based on source and desti-
nation IP address.
3. Censorship Technique 1: DNS injection For DNS requests that are blocked by the
GFW, the GFW will respond with a fake DNS
record to prevent the client from reaching the
requested content.
4. 3 steps of DNS injection 1) DNS probe is sent to a DNS resolver
2) The probe is checked against the blocklist
3) A fake DNS A record response is sent back
if the request matches the blocklist. The direct
domain can be blocked, or specific domain
keywords can be blocked.
5. How many DNS Censorship Techniques 5
are there?
1/5
, CS6250 Module 10 Practice Exam 2026
Guide
6. 1. Packet dropping all network traflc going to a set of specific IP
addresses is discarded
Pros: (easy to implement, low cost)
Cons: (maintain a long blocklist, overblock-
ing)
7. 2. DNS Poisoning When a DNS receives a query for resolving
hostname to IP address - if there is no answer
returned or an incorrect answer is sent to
redirect or mislead the user request
Pros: (No overblocking)
Cons: (Blocks the entire domain)
8. 3. Content inspection all traflc traverses a proxy and is inspect-
ed for objectionable content, if matches ->
dropped
Pros: (precise censorship, flexible)
Cons: (not scalable)
9. 4. Blocking with reset sends a TCP (RST) to block individual connec-
tions that contain requests with objectionable
content.
10. 5. Immediate reset suspends traflc coming from a source imme-
diately, for a short period of time
11. What is overblocking? If two websites share the same IP address
and the intention is to only block one of them,
there's a risk of blocking both
12.
2/5
