Which security control acts as a barrier by filtering traffic according to security rules?

Which security control acts as a barrier by filtering traffic according to security rules?

• A. Encryption
• B. DNS
• C. Firewall
• D. Two-factor authentication

Answer: (C)

Filtering traffic according to security rules is what a firewall does. It sits at the network boundary and enforces a policy by inspecting each packet or connection and deciding whether to allow or block it based on rules like source/destination IP, port, and protocol. This creates a barrier that prevents unauthorized access while permitting legitimate traffic, which is exactly the role described. Encryption protects the contents of data so it can’t be read if intercepted, but it doesn’t decide which traffic to allow or block. DNS translates domain names to IP addresses, not traffic filtering. Two-factor authentication strengthens user login security, but it doesn’t filter network traffic between systems.

Filtering traffic according to security rules is what a firewall does. It sits at the network boundary and enforces a policy by inspecting each packet or connection and deciding whether to allow or block it based on rules like source/destination IP, port, and protocol. This creates a barrier that prevents unauthorized access while permitting legitimate traffic, which is exactly the role described.

Encryption protects the contents of data so it can’t be read if intercepted, but it doesn’t decide which traffic to allow or block. DNS translates domain names to IP addresses, not traffic filtering. Two-factor authentication strengthens user login security, but it doesn’t filter network traffic between systems.