A firewall is a guard b/w your computer or your internal network and the outside world or the Internet. A particular firewall implementation may use one or more these types of methods :
- Packet filtering
- Stateful packet filtering
- User authentication
- Client application authentication
A firewall will filter incoming packets based upon these parameters such as packet size, source IP address, protocol, and destination port. Linux and Windows operating systems come up with a simple firewall. There are two best personal firewall solution provider for individual PCs
These firewalls are meant for individual machines. There are many advanced solutions available for network protection.
In an organizational setting, you can establish a dedicated firewall b/w your network and the outside world. This may be a router that also has built-in firewall capabilities. (Cisco Systems is one company that is well-known for high-quality routers and firewalls.) Alternatively, it might be a server that is dedicated to run firewall software. There are many numbers of firewall solutions that you can examine.