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1. Network Security and Protocols

2. Threats
 Prevent users from accessing the required
resources for performing their task
Types of Threats
Internal External

3. Internal Threats
• Malicious practices done by the local networks users
that do not allow efficient sharing of the network
resources
• Common internal threats are:
– Unauthorized Access
– Data Destruction
– Administrative Access
– System Crash/Hardware Failure
– Virus

4. Protecting from Internal Threats
• Methods of protecting internal threats largely dependent
on policies rather than technology
• To protect the network from internal threats you need to
implement:
– Passwords
– User Account Control – creating groups
– Policies
– Fault Tolerance

5. External Threats
• External threats can exist in two forms:
– Attacker manipulates the user to gain access to the
network
– Hacker at a remote location uses technical methods to
gain illegal access to your network
• Common external threats are:
– Social Engineering
– Hacking – internet worms or other internet hacking tools

6. Protecting from External Threats
• Securing network from external threat is a competition
between hackers and security people
• To protect the network from external threats you need
to provide:
– Physical protection – lock the server
– Firewalls
– Encryption –IPSec ,SSL
– Authentication – Kerberos, PAP, CHAP
– Public Keys and Certificates
– VLAN

7. Need for Network Security
• Network security - Mechanism that protects the
network resources from being attacked by the outside
world
• Hackers constantly look out for loopholes in the
network security and snoop into a network
• Spyware and other adware program get installed into
your computer and start transmitting private
information
• IP snooping allows monitoring of network traffic that is
sent over the internet

8. Security Attacks - I
• Break the security barrier of the network and access the
network resources
Types of Security
Attacks
Active Passive

9. Implementing External Network
Security - I
• Implementing external network security was not necessary
while dial up connections were used
• Arrival of high speed internet connection has completely
changed security aspect for home computers
• Users who use Asymmetric digital subscriber line (ADSL) or
a cable modem is the main target for the hackers
• Windows XP now has an Internet Connection Firewall (ICF)
available

10. Implementing External Network
Security - II
• SOHO routers are connected to provide security to
networked systems sharing a single Internet connection
• Large networks employ a dedicated firewall between a
gateway router and the protected network
• A demilitarized zone (DMZ) can also be implemented to
prevent access to the network

11. Cryptography
• Cryptography is a science that deals with securing
information
• Objectives of Cryptography are:
– Message Confidentiality
– Message Integrity
– Message Authentication
– Message Nonrepudiation – solves the issues related to
disputes beteween sender and receiver
– Entity Authentication

12. Types of Cryptosystems
• Cryptographic systems consists of algorithms and
procedures used for encrypting the messages
• Types of cryptographic systems:
– Symmetric Cryptographic Systems
– Asymmetric Cryptographic Systems
• Symmetric Cryptographic Systems use same keys for
encryption and decryption
• Asymmetric Cryptographic Systems use two keys, one for
encryption and other for decryption

13. Encryption/Decryption
• Encryption refers to conversion of plain text into cipher
text
• Cipher algorithm is used to transform plain text into
cipher text
• Different types of traditional ciphers used to encode the
message fall in to two broad categories:
– Substitution ciphers
– Transposition ciphers

14. Public Key Encryption/Decryption
• Uses a combination of two keys the private key and
the public key (Asymmetric)
• Private key is known only to the receiver of the
message

15. Secret Key Encryption / Decryption
• Uses the same key to encrypt and decrypt the message
(Symmetric)
• Algorithm used for decrypting the message is inverse of
algorithm that is used to encrypt message

16. Digital Signatures - I
• Used to authenticate the origin of the document
• Come under the asymmetric cryptography category
• Can be accomplished in two ways:
– Signing the document
– Signing the digest of the document

17. Digital Signature - II
• Signing the document
• Signing the digest

18. Digital Signature - III
• Signing the Document – public and private
keys of the sender are used for encrypting and
decrypting the document
• Signing the digest – used when the message
to be sent is long. Creates a digest of the
message using the hash function and then sign
it

19. Authentication Protocol
• Authentication is a process by which the identity of the
concerned party is identified before starting the
communication process
• Data traffic is encrypted using symmetric key
cryptography for performance reasons
• Public key cryptography is used for developing
authorization protocols as well as creating a session key

20. Authentication based on Shared Secret
Key
• Challenge response protocols used for authentication using
shared secret key

21. Authentication using Kerberos
• Three types of servers involved in Kerberos protocol:
– Authentication Server (AS)
– Ticket-Granting Server (TGS)
– Real Server

22. Authentication using Public – Key
Cryptography
• Certification Authority : Organization that binds a public
key to an entity and issues a certificate

23. Firewall - I
• Firewall is a system that blocks all unwanted and
unauthorized access of the system resources
• Firewall can be set using a router, switch, or a bridge
• Firewall is basically present at the junction point or
gateway between two networks like a private and public
network
• Firewalls can be hardware or software
• Basic types of firewalls are:
– Packet-Filter Firewalls
– Proxy Firewalls

24. Types of Firewall
• Packet filter Firewall – forward or blocks the
packets depending source and destination IP
address, port address or type of protocol used
(TCP or UDP). Collects the information from
the network and transport layer headers
• Proxy Firewall – filters the data at application
layer e.g. online book

25. Firewall - II
• Demilitarized Zones in Firewall
– Network that is usually present between an internal and
external network of an organization
– DMZ host provides services for external networks thus
providing cover for internal networks against intruders

26. VLAN - I
• Individual broadcast domains created by the switch are
called virtual LANs.
• Different characteristics used to group stations in a VLAN
are:
– Port Numbers
– MAC addresses
– IP addresses
– Multicast IP Addresses
– Combination
• IEEE standard 802.1Q defines format of frame tagging in
VLAN

27. VLAN - II
• VLAN can be configured in three ways: Manual,
Automatic, and Semiautomatic
• Three methods used for communication between
switches are:
– Table Maintenance
– Frame tagging
– Time Division Multiplexing (TDM)
• Advantages of VLAN are:
– Network Management
– Creating Virtual Work Groups
– Security

28. Fault Tolerance and Redundancy
• Shared data of a network should have better protection
rather than having to restore the backups with difficulty
• The capability of a server to continue operating in case
of a hardware failure is known as fault tolerance
• To implement fault tolerance you have to make the data
redundant on the serving system

29. RAID
• RAID is a technology that uses a collection of hard disks
to share and replicate data
• Different levels of RAID are RAID 0, 1, 2, 3, 4, 5, 6, 0+1,
10, 53 and linear RAID

30. Network-Attached Storage (NAS)
• Used for implementing a server just for file sharing
• A prebuilt system usually running LINUX with Samba and/
or Network File System (NFS)
• Devices have DHCP enabled and require very little or no
configuration to run

31. Storage area network (SAN)
• SAN is a network whose
primary aim is to transfer data
between disk arrays, tape
drives and servers
• The various SAN components
are:
– Fiber channel Switches
– Hosts and Host Bus Adapters
– Storage Devices
– Cabling and Cable Connectors

32. Tape Backup
• Tape backup becomes essential incase of a hardware
crash or damage to the server
• Magnetic tape is the oldest method of storing data from
the computer
• Tape backup options fall in to three major groups:
– Quarter-inch tape (QIC)
– Digital Audio Tape (DAT)
– Digital Linear Tape (DLT)

33. Perfect Server - I
• Network that shares data requires specialized hardware
so as to share data as fast as possible
• Hardware requirement for Speed
– Fast NICS : Increasing the data throughput and making it
do more than one task at a time
– Faster Drives : Using a PATA or a SCSI drive and
implementing RAID 5 for data protection

34. Perfect Server - II
• Servers require reliability, speed as well as data
protection
• Good Power
• Antivirus Program
• Environment

35. Hardware Requirement for speed
• The hardware requirements for a server and a
workstation differ from each other completely
• Workstations do not require the speed, reliability and
data backup. Servers on the other hand require
reliability, speed, as well as data protection
• The two things that can make the server provide good
speed are:
– Fast NICs
– Fast Drives

36. Reliability - I
• A steady AC power supply is to be provided to all the
systems
• The different methods of providing good power are:
– Dedicated Circuits
– Surge suppressors
– Uninterruptible Power Supply (UPS)
– Backup Power
• Another problem along with faulty power is computer
viruses

37. Reliability - II
• Five typical types of viruses are:
– Boot sector
– Executable
– Macro
– Trojan
– Worm
• Damage due to virus attacks can be prevented by not
allowing the virus from entering the system
• Necessary to provide a good environment for the server
to improve its reliability

38. Protocols
• Different protocols are used at different layers of the OSI
model for providing security to the users
• The different protocols used are:
– Secure Socket Layer (SSL)
– Internet Protocol Security (IPSec)
– Point-to-Point Tunneling Protocol (PPTP)
– Point-to-Point Protocol (PPP)
– Serial Line Interface Protocol (SLIP)

39. SLIP
• Serial Line Internet Protocol (SLIP) is used to connect the
computer to the Internet using serial connection such as
the dial-up modem
• Serial Line Internet Protocol was designed for Data link
protocol for telephony
• However, SLIP only supported TCP/IP and not NetBEUI or
IPX network.

40. PPP - I
• One of the common protocols for point to point access
• PPP addressed all of the shortcomings of SLIP
• Different services provided by PPP are as follows:
– Defines the format of the frames to be exchanged
between devices.
– Defines how the devices can negotiate for establishment
of link and exchange of data
– Defines how network layer data is encapsulated in the
data link frame.
– Defines how the devices can authenticate each other

41. PPP - II
• Provides multiple network layer services that support
different network layer protocols.
• Provides connection over multiple links.
• Provides network address configuration which is useful
incase a user needs a temporary network address to
connect to the Internet

42. PPTP
• Network protocol that allows secure transfer of data
from a remote client to a private server
• It is the Microsoft VPN encryption protocol
• The three processes involved in PPTP are:
– PPTP connection and communication
– PPTP control connection
– PPTP data tunnelling

43. IPSec
• Protocol set that was developed by Internet Engineering
Task Force (IETF) for providing security to a packet at the
network level
• IPSec operates in two modes:
– Transport Mode
– Tunnel Mode

44. SSL
• SSL is a protocol developed by Netscape for transmitting
private documents over the Internet.
• Web pages that use SSL have URLs starting with https
• Different services provided by SSL for the data received
by application layer are:
– Fragmentation
– Compression
– Message Integrity
– Confidentiality
– Framing