Types of Firewalls
A firewall filters and inspects network traffic to block unauthorized access, protect against cyber attacks, and prevent tampering with data. It safeguards a network from threats by controlling which devices can connect to it and how much data each device is allowed to send and receive. It also monitors and blocks cyberattacks like distributed denial of service (DDoS) attacks. Firewalls can be software or hardware, but they are typically installed on individual hosts. As a result, software firewalls require that each host is protected individually and may use up CPU and RAM resources. Hardware firewalls are able to monitor more devices at once and offer greater scalability for the protection of large networks.
Packet filtering firewalls are the most basic type of firewall, working at the network layer of OSI (Open Systems Interconnection) Layers 3 and 4, examining data packets and determining whether to permit or deny them based on pre-established security rules. They examine surface-level information like the destination and origin IP address of each packet, as well as port numbers and other surface-level details without examining the contents of each data packet. This type of firewall can be effective for small businesses that need basic protection against existing cyber threats.
Circuit-level gateways are a more advanced form of firewall, requiring only that each data packet pass through by verifying that the transmission control protocol (TCP) handshake is valid. They are highly resource-efficient and can be a good option for small businesses that require quick and simple approval or rejection of incoming traffic. Stateful inspection firewalls are more complex than either packet filtering or circuit monitoring, allowing them to examine the context of each data packet and check for malicious code within the payloads of data packets. They can be more effective than packet filtering or circuit monitoring, but exact a larger toll on the performance of a network.