Updated: May 17
In computing, a firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted internal network and untrusted external network, such as the Internet.
A firewall is software used to maintain the security of a private network. Firewalls block unauthorized access to or from private networks and are often employed to prevent unauthorized Web users or illicit software from gaining access to private networks connected to the Internet. A firewall may be implemented using hardware, software, or a combination of both.
The exponential growth of the internet and the resulting increase in connectivity of networks, however, meant that filtering network traffic by IP address alone was no longer enough. Static packet-filtering firewalls, which examine packet headers and use rules to make decisions about what traffic to let through, arguably became the most important part of every network security initiative by the end of the last century.
When there is a proxy firewall in place, both the client and the server are forced to conduct the session through an intermediary — a proxy server that hosts an application layer firewall. Now, each time an external client requests a connection with an internal server (or vice versa), the client will open a connection with the proxy instead. If the connection meets the criteria in the firewall rule base, the proxy will open a connection to the requested server.
Because the firewall is placed in the middle of the logical connection, it can watch traffic for any signs of malicious activity at the application layer.
A firewall is recognized as the first line of defense in securing sensitive information. For better safety, the data can be encrypted.Firewalls generally use two or more of the following methods:
Packet Filtering: Firewalls filter packets that attempt to enter or leave a network and either accept or reject them depending on the predefined set of filter rules.
Application Gateway: The application gateway technique employs security methods applied to certain applications such as Telnet and File Transfer Protocol servers.
Circuit-Level Gateway: A circuit-level gateway applies these methods when a connection such as Transmission Control Protocol is established and packets start to move.Proxy Servers: Proxy servers can mask real network addresses and intercept every message that enters or leaves a network.
Stateful Inspection or Dynamic Packet Filtering: This method compares not just the header information, but also a packet’s most important inbound and outbound data parts. These are then compared to a trusted information database for characteristic matches. This determines whether the information is authorized to cross the firewall into the network.
This change in architecture has caused some security experts to warn that, while firewalls still have an important role to play in keeping a network secure, modern network perimeters have so many entry points and different types of users that stronger access control and security at the host are required. The need for an even greater multilayer approach has led to the emergence of what vendors are calling next-generation firewalls.
Do firewalls have an IP address?
Firewalls are also used for Network Address Translation (NAT). This allows a network to use private IP addresses that are not routed over the Internet. … In addition to port and IP address rules, firewalls can have a wide variety of functionality. They can also act as caching servers, VPNs, routers, and more.
What is a Layer 7 firewall?
Layer 7, the application layer of the OSI (Open System Interconnection) Model, supports application and end-user processes, such as HTTP and SMTP. … Many application-layer firewalls allow you to create filters to intercept, analyze or modify traffic specific to your network.
What is a firewall in simple terms?
A system designed to prevent unauthorized access to or from a private network.Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets.
What are the 3 types of firewalls?
Right now, there are five different types of firewall architectures, broadly speaking:
Stateful inspection firewalls.
Application-level gateways (a.k.a. proxy firewalls)