Stateful Firewalls: These firewalls track the state of network connections (like TCP handshakes). They understand the context of a conversation, allowing return traffic for established connections while blocking unsolicited inbound packets. This is a key security advantage.
Stateless Firewalls: These firewalls examine packets individually, based only on header information like source/destination IP and ports. They don't "remember" past packets or the state of a connection.
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A) Filtering incoming and outgoing packets based solely on predefined IP addresses and port numbers without maintaining connection information: This describes a stateless firewall.
B) Allowing return traffic for established connections while automatically denying unsolicited inbound packets based on the state of the connection: This is the core advantage of a stateful firewall. It prevents outside systems from initiating connections to internal systems unless there was an initial request from inside.
C) Implementing Network Address Translation (NAT) to obscure internal network structures from external entities: NAT is a network function, often implemented in firewalls, but it's not the fundamental security advantage that distinguishes stateful from stateless firewalls. Both can implement NAT.
D) Utilizing Access Control Lists (ACLs) to permit or deny traffic based on static rule sets without context of ongoing sessions: This describes a stateless firewall.