Firewalls and network protection in Intro to Computing - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

How does a firewall decide which network traffic to allow?

Imagine a security guard checking people entering a building. How does a firewall act like this guard when deciding which data packets to allow through a network?

A It randomly blocks half of the incoming data to reduce network load.

B It checks rules based on source, destination, and type of data to allow or block traffic.

C It allows all data except those from unknown websites.

D It only blocks data if the user manually approves each packet.

💡 Hint

Think about how a guard uses a list of allowed visitors rather than guessing randomly.

A firewall uses a set of rules to check details like where data comes from, where it is going, and what kind of data it is. This helps it decide to allow or block the traffic, similar to a guard checking IDs.

❓ trace

intermediate

Trace the firewall packet filtering process

Follow the steps a firewall takes to filter a packet with source IP 192.168.1.10, destination IP 10.0.0.5, and port 80. The firewall rules allow HTTP traffic (port 80) only from 192.168.1.0/24 subnet.

A Packet allowed because source IP is in allowed subnet and port is 80.

B Packet blocked because destination IP is outside allowed subnet.

C Packet allowed because destination IP matches the firewall's IP.

D Packet blocked because port 80 is not allowed.

💡 Hint

Check if the source IP fits the allowed range and if the port matches the allowed service.

The firewall checks if the source IP 192.168.1.10 is in the 192.168.1.0/24 subnet and if the port is 80 (HTTP). Both conditions are true, so the packet is allowed.

❓ identification

advanced

Identify the type of firewall from its description

A firewall inspects the contents of data packets deeply, checking the actual data and not just headers, to detect malicious content. What type of firewall is this?

A Deep packet inspection firewall

B Stateful inspection firewall

C Proxy firewall

D Packet-filtering firewall

💡 Hint

Think about which firewall looks inside the data, not just the envelope.

Deep packet inspection firewalls analyze the actual data inside packets to detect threats, unlike simpler firewalls that only check headers or connection states.

❓ Comparison

advanced

Compare stateful and stateless firewalls

Which statement correctly compares stateful and stateless firewalls?

A Neither stateful nor stateless firewalls check packet headers.

B Stateless firewalls track connection states; stateful firewalls check packets individually without context.

C Both stateful and stateless firewalls track connection states but differ in speed.

D Stateful firewalls track connection states; stateless firewalls check packets individually without context.

💡 Hint

Think about whether the firewall remembers past packets or treats each one alone.

Stateful firewalls keep track of active connections and use this context to filter packets, while stateless firewalls examine each packet separately without memory of past packets.

🚀 Application

expert

Determine the effect of firewall rule order on traffic filtering

A firewall has these rules in order:
1. Block all traffic from IP 203.0.113.5
2. Allow all traffic to port 22 (SSH)
3. Allow all traffic from IP 203.0.113.5

If a packet comes from IP 203.0.113.5 to port 22, what happens?

A The packet is allowed because the last rule allows traffic from the IP.

B The packet is allowed because the allow rule for port 22 overrides the block.

C The packet is blocked because the first matching rule blocks the IP before the allow rule.

D The packet causes an error because conflicting rules exist.

💡 Hint

Remember firewalls usually apply rules in order and stop at the first match.

The firewall checks rules top to bottom. The first rule blocks traffic from 203.0.113.5, so the packet is blocked before reaching the allow rules.