Chapter 8:-FIREWALL

What is Firewall?

A firewall is a dedicated appliance, or software running on another computer, which inspects network traffic passing through it, and denies or permits passage based on a set of rules.

Types of firewall

Packet Filter Rules

Firewall Basing

 Bastion host

A system that has been hardened to resist attack, and which is installed on a network in such a way that it is expected to potentially come under attack. Bastion hosts are often components of firewalls, or may be "outside" Web servers or public access systems. Generally, a bastion host is running some form of general purpose operating system (e.g., Linux, VMS, Windows) rather than a ROM-based or firmware operating system like commercial routers do. Bastion hosts are also referred to as ''gateway hosts.''

Bost-based firewall
-used to secure individual host
-available in/add-on for many O/S
-filter packet flows
-often used on servers
-advantages:
--taylored filter rules for specific host needs
--protection from both internal / external attacks
--additional layer of protection to org firewall

Personal firewall
- for providing protection to desktop PCs and small networks connected to the Internet.
- a software program used to guard and protect a computer or a network while they are connected to the Internet.
- Generally, home and small networks
-A personal firewall enforces the security policies of a computer or a network by intercepting and examining the data transportation (data packets) over the network.
- Either it allows all the data packets to enter the network except those meeting a specified criteria (restricted ones) or it deny all the data packets from entering except those that are allowed.

VPN
- a computer network that is implemented in an additional software layer (overlay) on top of an existing larger network for the purpose of creating a private scope of computer communications -
-One common application is to secure communications through the public Internet, but a VPN does not need to have explicit security features such as authentication or traffic encryption. For example, VPNs can also be used to separate the traffic of different user communities over an underlying network with strong security features, or to provide access to a network via customized or private routing mechanisms.

-VPNs are often installed by organizations to provide remote access to a secure organizational network.
-Generally, a VPN has a network topology more complex than a point-to-point connection.

Distributed Firewall

• A distributed firewall configuration involves standalone firewall devices plus host-based firewalls, personal firewall working together under a central administrative control.
• Administrators can configure host-resident firewalls on hundreds of servers and workstation as well as configuring personal firewalls on local and remote user systems. Tools let the network administrator set policies and monitor security across the entire network.