.:: || Firewall || ::.

Types of firewall

• 1. Packet filtering firewall


• 2. statefull inspection firewall


• 3. Application level gateway (application proxy)


• 4. circuit level gateway

Type 1: Packet filtering firewall


Packet filters act by inspecting the "packets" which represent the basic unit of data transfer between computers on the Internet. If a packet matches the packet filter's set of rules, the packet filter will drop (silently discard) the packet, or reject it (discard it, and send "error responses" to the source).

This type of packet filtering pays no attention to whether a packet is part of an existing stream of traffic (it stores no information on connection "state"). Instead, it filters each packet based only on information contained in the packet itself (most commonly using a combination of the packet's source and destination address, its protocol, and, for TCP and UDP traffic, the port number).



Type 2: Stateful Inspection Firewall


Third generation firewalls in addition regard placement of each individual packet within the packet series. This technology is generally referred to as a stateful packet inspection as it maintains records of all connections passing through the firewall and is able to determine whether a packet is either the start of a new connection, a part of an existing connection, or is an invalid packet. Though there is still a set of static rules in such a firewall, the state of a connection can in itself be one of the criteria which trigger specific rules.

This type of firewall can help prevent attacks which exploit existing connections, or certain Denial-of-service attacks.

Type 3: Application Proxy Firewall & Type 4: Circuit-level Proxy Firewall


Firewall hosting

• 1. Bastion host = single firewall that cover a network territory


• 2. Host-base = single firewall protect a single workstation/server

VPN

• Create a secure LAN connection through an internet.


• outsider will tgought that we in a LAN network but actually we use the internet.

Distributed firewall

• A firewall installed per subnet in a network

A feature of distributed firewalls:

• The ability to populate servers and end-users machines, to configure and "push out" consistent security policies helps to maximize limited resources.


• secure critical servers on the network preventing intrusion by malicious code and "jailing" other such code by not letting the protected server be used as a launch pad for expanded attacks.