Kerberos

University Institute of Engineering (UIE)
Department of Computer Science and Engineering (CSE)
Firewalls
www. cuchd.in Campus : Gharaun, Mohali

Internet & Security
The internet is one of the term which booms in all over the
world. Everyone uses computers & networks for various
purposes.
While using the networks, we face one biggest problem is the
SECURITY.
The internet is one of the term which booms in all over the
world. Everyone uses computers & networks for various
purposes.
While using the networks, we face one biggest problem is the
SECURITY.

Firewall
Firewall provides security from the malicious sources, and
it blocks the intruders which can harm our computer
systems and our valuable data.

Firewall
What is firewall ?
Need of firewall
Types of firewall
Types of firewall techniques
Conclusion

Firewall
A firewall may be a hardware, software or a
combination of both that is used to prevent
unauthorized program or internet users from
accessing a private network or a single
computer.
All message entering or leaving the intranet
pass through the firewall, which examines each
message & blocks those that do not meet the
specified security criteria.

Why need firewall/Roles/Ojbective of firewalls
To protect confidential information from those who do not explicitly
need to access it.
To protect our network & its resources from malicious users &
accidents that originate outside of our network.
Workplace web browsing restrictions: Employers can prevent
employees from using company networks to access certain services and
content, such as social media.
Infiltration from malicious actors: Undesired connections from an
oddly behaving source can be blocked. This can prevent eavesdropping
and advanced persistent threats (APTs).

Types of Firewall
Hardware firewall
Software firewall

Hardware Firewall
It is a physical device.
It can be installed between the modem and computer.
It can be incorporated into a broadband router being used
to share the internet connection.
Protect an entire network.
Usually more expensive, harder to configure
E.g.- Cisco pix, netscreen, watchfuard etc.

Harware Firewall Advantages
Uses very little system resources.
More secure
Enhanced security control
Dedicated hardware firewalls are typically more reliable
Easy to disable or remove
Work independently of associated computer system.

Hardware Firewall Disadvantages
Install process is more demanding both physically
and mentally.
Takes up physical work space
More expensive
Harder to upgrade and repair

Software Firewall
It is a software application.
It is installed onto the computer system that you
wish to protect.
Protect a single computer
This is usually the computer with modem attached to it.
Usually less expensive, easier to configure
E.g.- Norton internet security, MacAfee internet
security etc.

Advantages of Software Firewall
Considerably cheaper or even free.
Simple to install and upgrade
Requires no physical changes to hardware or
network
Ideal for home/family use
Takes up no physical space.

Disadvantages of Software Firewall
Software may crash or be incompatible with system
Can be difficult to completely disable & especially
remove
Software bugs may compromise security
Incompatibilities with OS.

Types of Firewall Techniques
 Packet filter
 Application gateway/proxy application gateway
 Circuit-level gateway
 Bastion host

Packet filter
 A packet filtering firewall is the most basic type of firewall.
It acts like a management program that monitors network
traffic and filters incoming packets based on configured
security rules.
 These firewalls are designed to block network
traffic IP protocols, an IP address, and a port number if a data
packet does not match the established rule-set.

Drawbacks of packet filtering technique
• Packet filtering rules can be complex.
• Logging facility is not provided by such firewall.
• If TCP/IP packet filtering is not implemented fully, it can
lead to security loop hole.
• Cannot handle RPC (remote produce calls)

Application gateway
In such type of firewall, remote host or network can interact
only with proxy server, proxy server is responsible for hiding
the details of the internal network i.e. intranet.
Users uses TCP/IP application, such as FTP &Telnet servers.
Application gateway firewalls are considered to be some of
the most secure firewalls available because of their capability
to inspect packets and ensure the packets are conforming to
application specifications.

Advantages of Application Gateway
Less complex filter rules
Cost effectiveness
Robust authentication & logging facility
Proxy authenticates only those services for which it is
configured/installed.

Circuit level gateway
It is a stand alone application.
It does not permit end-to-end TCP connection. it sets up 2
TCP connection:-
• Between itself and a TCP user on an inner host.
• Between itself and a TCP user on an outer host.

• Some associated benefits include: Comparatively
inexpensive than other firewalls.
• Provide anonymity to the private network.
• Monitor Transmission Control Protocol's (TCP) three way
handshake.
Advantage of Circuit level gateway

• A system identified by the firewall administrator as a
critical strong point in the network security.
• Generally, bastion hosts will have some degree of extra
attention paid to their security, may undergo regular
audits, and may have modified software.
• Eg. DNS (Domain Name System) server
• Email server
• FTP (File Transfer Protocol) server
• Honeypot
• Proxy server
• VPN (Virtual Private Network) server
• Web server
Bastion host

• To its advantage, this configuration requires the external
attack to compromise two separate systems, before the
attack can access internal data.
• In this way, the bastion host protects the data more fully
than the router alone.
Advantage of bastion host

• It can be difficult to choose between different firewall
types. Adding to the difficulty is the fact that many
organizations need to use multiple firewalls to create
strong network segmentation for a “defense in depth”
strategy.
• Using firewalls with conflicting rules can cause legitimate
traffic to be dropped, resulting in poor network
performance and inefficiency.
How Do I Know Which Type of Firewall Is Right for My
Organization?

Conclusion
One of the best things about a firewall is that it stops
anyone on the outside from logging onto a computer in your
private network. While this is a big deal for businesses. Still,
putting a firewall in

References
• https://www.simplilearn.com/what-is-kerberos-article
• https://www.geeksforgeeks.org/kerberos/
• https://docs.axway.com/bundle/APIGateway_762_Integratio
nKerberos_allOS_en_HTML5/page/Content/KerberosIntegrat
ion/kerberos_overview.htm
• https://www.cs.ait.ac.th/~on/O/oreilly/tcpip/firewall/ch04_
02.htm

E- Books Recommended
• https://www.jigsawacademy.com/blogs/cyber-
security/kerberos-authentication/
• https://www.worldcat.org/title/kerberos-the-definitive-
guide/oclc/780425105

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