Firewalls monitor and filter network traffic based on security policies. There are different types of firewalls that use various methods like packet filtering, application-level gateways, stateful inspection, and more. Firewalls are necessary to protect networks from threats and work by allowing approved traffic while blocking dangerous traffic according to pre-set policies. They defend networks by detecting and responding to malware and other attacks across the entire system.

1. FIREWALL
…Different types of firewall…
ABSTRACT
This includes description about different types of
firewalls. Its necessity & working procedure etc.
Supervised By
Pranab Bandhu Nath
(Senior Lecturer)
CSE Department
City University, Dhaka
Submitted By
Shamima Akther| ID - 1834902616
CSE 317 : Computer Networks

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. A firewall’s main purpose is to allow non-threatening traffic in and to keep dangerous
traffic out.
Firewall History
Firewalls have existed since the late 1980’s and started out as packet filters, which were
networks set up to examine packets, or bytes, transferred between computers. Though packet
filtering firewalls are still in use today, firewalls have come a long way as technology has
developed throughout the decades.
Types of Firewalls:
Firewall types can be divided into several different categories based on their general structure
and method of operation. Here are eight types of firewalls:
• Packet filtering
A small amount of data is analyzed and distributed according to the filter’s standards.
As the most “basic” and oldest type of firewall architecture, packet-filtering firewalls basically
create a checkpoint at a traffic router or switch. The firewall performs a simple check of the data
packets coming through the router—inspecting information such as the destination and
origination IP address, packet type, port number, and other surface-level information without
opening up the packet to inspect its contents.
If the information packet doesn’t pass the inspection, it is dropped.
The good thing about these firewalls is that they aren’t very resource-intensive. This means they
don’t have a huge impact on system performance and are relatively simple. However, they’re
also relatively easy to bypass compared to firewalls with more robust inspection capabilities.
• Application-level gateways (a.k.a. proxy firewalls)
Network security system that protects while filtering messages at the application layer.
Proxy firewalls operate at the application layer to filter incoming traffic between your network
and the traffic source—hence, the name “application-level gateway.” These firewalls are
delivered via a cloud-based solution or another proxy device. Rather than letting traffic connect
directly, the proxy firewall first establishes a connection to the source of the traffic and inspects
the incoming data packet.
This check is similar to the stateful inspection firewall in that it looks at both the packet and at
the TCP handshake protocol. However, proxy firewalls may also perform deep-layer packet

3. inspections, checking the actual contents of the information packet to verify that it contains no
malware.
Once the check is complete, and the packet is approved to connect to the destination, the proxy
sends it off. This creates an extra layer of separation between the “client” (the system where the
packet originated) and the individual devices on your network—obscuring them to create
additional anonymity and protection for your network.
If there’s one drawback to proxy firewalls, it’s that they can create significant slowdown because
of the extra steps in the data packet transferal process.
• Stateful inspection
Dynamic packet filtering that monitors active connections to determine which network packets to
allow through the Firewall.
These firewalls combine both packet inspection technology and TCP handshake verification to
create a level of protection greater than either of the previous two architectures could provide
alone.
However, these firewalls do put more of a strain on computing resources as well. This may slow
down the transfer of legitimate packets compared to the other solutions.
• Next Generation Firewall (NGFW)
Deep packet inspection Firewall with application-level inspection.
• Software firewalls
Software firewalls include any type of firewall that is installed on a local device rather than a
separate piece of hardware (or a cloud server). The big benefit of a software firewall is that it's
highly useful for creating defense in depth by isolating individual network endpoints from one
another.
However, maintaining individual software firewalls on different devices can be difficult and
time-consuming. Furthermore, not every device on a network may be compatible with a single
software firewall, which may mean having to use several different software firewalls to cover
every asset
• Hardware firewalls
Hardware firewalls use a physical appliance that acts in a manner similar to a traffic router to
intercept data packets and traffic requests before they're connected to the network's servers.
Physical appliance-based firewalls like this excel at perimeter security by making sure malicious
traffic from outside the network is intercepted before the company's network endpoints are
exposed to risk.
The major weakness of a hardware-based firewall, however, is that it is often easy for insider
attacks to bypass them. Also, the actual capabilities of a hardware firewall may vary depending

4. on the manufacturer—some may have a more limited capacity to handle simultaneous
connections than others, for example.
• Cloud firewalls
Whenever a cloud solution is used to deliver a firewall, it can be called a cloud firewall, or
firewall-as-a-service (FaaS). Cloud firewalls are considered synonymous with proxy firewalls by
many, since a cloud server is often used in a proxy firewall setup (though the proxy doesn't
necessarily have to be on the cloud, it frequently is).
The big benefit of having cloud-based firewalls is that they are very easy to scale with your
organization. As your needs grow, you can add additional capacity to the cloud server to filter
larger traffic loads. Cloud firewalls, like hardware firewalls, excel at perimeter security.
• Circuit-level gateways
As another simplistic firewall type that is meant to quickly and easily approve or deny traffic
without consuming significant computing resources, circuit-level gateways work by verifying the
transmission control protocol (TCP) handshake. This TCP handshake check is designed to make
sure that the session the packet is from is legitimate.
While extremely resource-efficient, these firewalls do not check the packet itself. So, if a packet
held malware, but had the right TCP handshake, it would pass right through. This is why circuit-
level gateways are not enough to protect your business by themselves.
Need of Firewalls
Firewalls, especially Next Generation firewall 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 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.
Working of Firewalls
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.