MENU
Which of the following firewall types operates at the Network layer of the OSI model and can filter
data by port, interface address, source address, and destination address?
Packet filtering is a method that allows or restricts the flow of specific types of packets to provide
security. It analyzes the incoming and
outgoing packets and lets them pass or stops them at a network interface based on the source and
destination addresses, ports, or
protocols. Packet filtering provides a way to define precisely which type of IP traffic is allowed to
cross the firewall of an intranet. IP packet
filtering is important when users from private intranets connect to public networks, such as the
Internet.
Answer option B is incorrect. An application gateway firewall applies security mechanisms to specific
applications, such as FTP and Telnet
servers. This is very effective, but can impose a performance degradation.
Answer option A is incorrect. A circuit-level gateway firewall applies security mechanisms when a
TCP or UDP connection is established. Once
the connection has been made, packets can flow between the hosts without further checking.
Answer option C is incorrect. A proxy server firewall intercepts all messages entering and leaving the
network. The proxy server effectively
hides the true network addresses.