 | What is a firewall? |
Technical Answer:
A firewall is a gateway that limits access between networks and enforces local security policy. It is a proxy server that filters and logs packets passing through it based upon rules. The term "firewall" can refer to either the program performing the screening or the computer it runs on. The firewalls main purpose is to disallow unauthorized or potentially dangerous material from entering a local network. In addition, the firewall can also limit access to resources on the Internet as a security measure, cache previously visited pages, log all traffic or specific traffic, and limit access to certain users. Usually, the firewall is deployed at the junction of a trusted private network and the internet.
There are several methods by which a firewall could function. As an application gateway the firewall applies security mechanisms to specific applications, such as FTP and Telnet servers. This method is very effective, but can impose a performance degradation. As a proxy server the firewall intercepts all messages entering and leaving the network. This method is used to hide network addresses. A firewall functioning as a packet filter looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Although difficult to configure, packet filtering is transparent to users and fairly effective in enforcing security protocols. Also, packet filtering is susceptible to IP spoofing. Circuit-level gateway is a method by which the firewall applies security mechanisms when a TCP or UDP connection is established. Once the connection has been established, packets can flow between the machines without further filtering. This saves system resources and speeds transmission speeds. In actual systems, firewalls use a combination of these methods.
Short Answer:
A firewall is a program that protects your compute...
Long Answer:
Once, the term firewall was used to describe a type of barrier used in construction. As the name ...