Stateful Inspection Firewalls

C.

The correct answer is C. Stateful packet filter firewall.

Firewalls are a type of security system used to protect computer networks from unauthorized access or attacks. They can be either hardware or software-based, and they work by filtering and monitoring incoming and outgoing network traffic based on a set of predefined rules.

Stateless packet filter firewalls (option A) examine individual packets of data without considering their context or relationship to other packets. They filter based only on the packet header information, such as the source and destination IP addresses and port numbers. However, they do not keep track of the state of connections between packets, making them less effective at preventing certain types of attacks, such as session hijacking.

PIX firewalls (option B) are a type of firewall that was developed by Cisco Systems. They provide more advanced features than basic packet filter firewalls, such as the ability to perform network address translation (NAT) and VPN connectivity. However, they are considered to be a legacy technology and have largely been replaced by more modern firewall solutions.

Stateful packet filter firewalls (option C) are a more advanced type of firewall that operates at the network and session layers of the OSI model. They are also known as dynamic packet filter firewalls or next-generation firewalls. They not only examine individual packets but also keep track of the state of connections between packets. This allows them to identify and block certain types of attacks, such as session hijacking, by comparing incoming packets to a database of previously seen packets and connections.

Virtual firewalls (option D) are a type of firewall that is implemented in a virtual environment, such as a virtual machine or cloud network. They operate much like physical firewalls but are designed to provide security in a more flexible and scalable way. Virtual firewalls can be configured and managed centrally, making them easier to deploy and maintain in large or distributed environments.

In summary, stateful packet filter firewalls (option C) are the type of firewall that increases the security of data packets by remembering the state of connections at the network and session layers as they pass through the filter.