Firewall

A firewall is a hardware-based network security system that controls the incoming and outgoing network traffic based applied rule set.

A firewall establishes a barrier between a trusted, secure internal network and another network (i.e.the internet) that is not assumed to be secured and trusted.

A firewall typically protects the internal network from the public networks, they are also used control access between specific network segment within a network.

More sophisticated firewalls block traffic from the outside to the inside, but permit users on the inside to communicate a more freely with the outside.

Firewalls are essential since they can provide a single block point security and auditing can be imposed.

Firewalls provide an important logging an auditing function often they provide summaries to the administrator about type/volume of traffic has been processed through.

Four General Techniques Of Firewall:

1.) Service Control:

Determine the type of internet service that can be accessed, inbound or outbound.

2.)Direction Control:

Determines the direction in which particular service requests are allowed to flow.

3.)User Control:

Controls access to a service according to which user is attempting to access it.

4.)Behavior Control:

Controls how particular services are used (eg: filter E-mail)

Types Of Firewall:

1.)Hardware and Software:

Firewalls can be either hardware or software but the ideal firewall configuration will consist of both.

2.)Packet-Filtering Routers:

)Applies a set of rules to each incoming IP packet and then forwards or discards the packet.
)Filter packet going in both directions.
)Two default policies (discard or forward)

3.)Access Control Lists(ACLS):

This was early firewalls implemented typically on routers. They are useful for scalability and performance, but can't read more than packet headers, which provide only rudimentary information about the traffic.

4.)Proxy Firewall:

Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network address.

5.)Application Gateway:

Applies security mechanisms to specific applications, such as FTP and TELNET servers. This is very effective but can impose performance degradation.

6.)Stateful Inspection Firewall:

This was the major evolutionary step. they classify track the state of traffic by monitoring all connection interaction until a connection a closed.

7.)Circuit-level Gateways:

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.

8.)Next Generation Firewall (NGFW):

Next-generation firewall filters network and internet traffic based upon the applications or traffic types using specific ports. Next-generation firewalls blend the features of a standard firewall with a quality of service(QoS) functionalities in order to provide smarter and deeper inspection.

Advantages: