Firewall

1. Computer Networks
CLASS NOTE-6
Lecturer
Pranab Bandhu Nath
Senior Lecturer
CSE Department
City University, Dhaka
STUDENT
NAME :MD HASNAIN
ID :1834902583
Department of CSE City University, Dhaka.

2. Firewall
A Firewall is a network security device that monitors and filters
incoming and outgoing network traffic based on an organization’s
previously established security policies. At its most basic, a firewall is
essentially the barrier that sits between a private internal network and
the public Internet.
What Firewalls Do:-
A Firewall is a necessary part of any security architecture and takes the
guesswork out of host level protections and entrusts them to your
network security device. Firewalls, and especially Next Generation
Firewalls, focus on blocking malware and application-layer attacks,
along with an integrated intrusion prevention system (IPS), these Next
Generation Firewalls can react quickly and seamlessly to detect and
react to outside attacks across the whole network. They can set policies
to better defend your network and carry out quick assessments to
detect invasive or suspicious activity, like malware, and shut it down.
Why Do We Need Firewalls:-
Firewalls, especially Next Generation Firewalls, focus on blocking
malware and application-layer attacks. Along with an integrated
intrusion prevention system (IPS), these Next Generation Firewalls are
able to react quickly and seamlessly to detect and combat attacks
across the whole network. Firewalls can act on previously set policies to
better protect your network and can carry out quick assessments to

3. detect invasive or suspicious activity, such as malware, and shut it
down. By leveraging a firewall for your security infrastructure, you’re
setting up your network with specific policies to allow or block
incoming and outgoing traffic.
Several types of firewalls:
Packet filtering:
The system examines each packet entering or leaving the network and
accepts or rejects it based on user-defined rules. Packet filtering is fairly
effective and transparent to users, but it is difficult to configure. In
addition, it is susceptible to IP spoofing.
Circuit-level gateway implementation:
This process 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.
Acting as a proxy server:
A proxy server is a type of gateway that hides the true network address
of the computer(s) connecting through it. A proxy server connects to
the internet, makes the requests for pages, connections to servers, etc.,
and receives the data on behalf of the computer(s) behind it. The
firewall capabilities lie in the fact that a proxy can be configured to
allow only certain types of traffic to pass (for example, HTTP files, or
web pages). A proxy server has the potential drawback of slowing

4. network performance, since it has to actively analyze and manipulate
traffic passing through it.
Web application firewall:
A web application firewall is a hardware appliance, server plug-in, or
some other software filter that applies a set of rules to an HTTP
conversation. Such rules are generally customized to the application so
that many attacks can be identified and blocked.
REFERENCE
https://www.checkpoint.com/
https://en.wikipedia.org/
https://www.forcepoint.com/