453 Network Security

slurpslapoutΔίκτυα και Επικοινωνίες

20 Νοε 2013 (πριν από 4 χρόνια και 7 μήνες)

127 εμφανίσεις

453 Network Security

Section 1: Introduction to Network

Dr. E.C. Kulasekere

Sri Lanka Institute of Information Technology


Text Books

Network Security: Private Communication
in a Public World, Charlie Kaufman,
Pearson Education Inc., 2002

Network Security: A Complete Reference

Roberta Bragg, Mark Rhodes
Keith Strassberg

Tata McGraw

Cryptography and Network Security/3e

William Stallings, Pearson Ed. 2003.


Foundations of computer and network security.

Access Control and Site Security.

Threats and vulnerabilities.

Attack Methods.

Technical defenses: authentication, operating
system security, firewalls, etc.

Elements of Cryptography.

Cryptographic Systems: SSL/TLS, VPNs,

Application Security: Electronic Commerce and

Syllabus …

Network vulnerability assessment and
intrusion detection.

Remediation methods, including backup
and repair strategies.

Business continuity planning and disaster
recovery planning

Legal issues, privacy, cyber war and cyber

Other Information

Web site:





Found at website.

All information will be updated on the
website since I am a visiting instructor.

Expectation from Students

Friendly atmosphere in class.

Student involvement in discussions.

Complete laboratory work in time.

Do individual assignments by yourself and
not copy.

Have an attitude that the course is for
learning and not for passing exams.

Outline For this Section

Computer Security, Laws and Crime

Attacks, services and mechanisms

Security attacks and security services

Methods of defense

Model for internetwork security, Internet
standards and Request for comments.

Cryptographic algorithms

Secure protocols

Authentication, access control.

Security is it a New Concept?

Lock the Doors and Windows. Control access

Role Based Access

Only Mom is allowed to


t talk to strangers

even if you see some
one you know Look beyond.


t share your secrets

keep sniffers at bay


t accept gifts from strangers

Play nice with others

Leave your valuables at home. Don

t steal

Keep your shots up to date

If you see something wrong, call the police.

Levels of Security

Information security

Early days, security was provided by physical
access restrictions.

With networking this changed.

Computer security

Restriction to shared resource

Physical security

Network security

Protection of data during transmission.

Infrastructure setup for security. Eg. Bastion

Are these definitions enough?

More Classifications

Three D’s of security

Detection: tool based by monitoring

Defense: patching and updating

Deterrence: laws and policy making

Classification based on business

Business agility

Return on investment

Risk management and business continuity

Customer confidence

Attack, Services and Mechanisms

Security attack: any action that will
compromise the security of information.

Security mechanism: A mechanism that is
designed to detect , prevent, or recover from
a security attack.

Security services: A service that enhances
the security of data processing systems and
information transfers. A security service
makes use of one or more security

Normal flow of Information



Security Attacks

Security Attacks …

Unauthorized party gets access to information

This is an attack on confidentiality

The attacker could be a person or program.

Eg. of this could be unauthorized copying of files.


Security Attacks …

The system is destroyed or becomes unavailable

This is an attack on availability.

This could be a destruction of a piece of hardware
or cutting a communication line.


Security Attacks …

An unauthorized party gains access to information
and also modifies it.

This is an attack on integrity of information.

Modification of program or date files to operate or
contain different information.


Security Attacks …

An unauthorized party injects fabricated information
into the system.

This is an attack on authenticity.

Examples of this is insertion of spurious messages,
addition of records to a file etc.


Attack Types

Passive Attack:

This type of attack does not involve the
parties concerned.

Does not alter the information flowing
between the parties.

Active Attack

This type of attack involves the other parties

The information flow is altered.

Passive Attack

This type of attacks are hard to detect since it does
not involve the other party or alter the data.

This kind of attack can be prevented rather than

Examples are Eavesdropping or monitoring of

The objective of the opponent is to obtain the
information that is being transmitted.

Release of message content

Opponent getting to
know the contents.

Traffic analysis

the link traffic profile and information
gathering is done by the opponent.

Active Attack

This is easier to detect since the
information stream is altered and involves
the other party.

Harder to prevent since no absolute
protection is available with the current
buggy systems.

Involves some modification of the data
stream or creation of a false stream.


The entity pretends to be a different
entity. Eg. Use a sniffer on a telnet stream


passive capture of data, alter and then

Security Services

Confidentiality (privacy)

is the protection of
transmitted data from passive attacks.

Authentication (who created or sent the data)

assuring that the communication is authentic.

Integrity (has not been altered)

will ensure that the
messages are received with no duplication,
insertion, modification. Reordering or replays.

Connection oriented service

addresses DoS and
modifications (duplication, insertion, modification and
reordering problems handled).

Connectionless service

deals with only individual
messages and only assures against modification. This is
because it only deals with individual packets.

Security Mechanisms


Physical separation

Temporal separation

Logical separation

cryptographic separation

combinations of all above

Share all or nothing

share via access limitations

share by capabilities (tokens)

limit use of an object

Relationship Between

Services and Mechanisms

A Model for Network Security

Design Issues in the Model

Design an algorithm for performing the security
related transformation. The algorithm should be
such that an opponent cannot defeat its purpose.

Generate the secret information to be used with the

Develop methods for the distribution and sharing of
the secret information.

Specify a protocol to be used by the two principles
that makes use of the security algorithm and the
secret information to achieve a particular security

Other Considerations

Network Design Considerations

Designing for acceptable risk.

Use of network models with security (LAN/WAN more
secure?, Dedicated/non
dedicated?, segregation and

Host hardening

Firewalls, Packet filtering

Choice of network devices

Choice of routers and other hardware

Routing protocols

Intrusion detection systems (IDS)

Host based IDS

Network based IDS

Security Highlighted

Kevin Mitnick

FBI arrested Kevin in February 1995

stealing 20,000 credit
card numbers
through the Internet. Valued at over one
million dollars.

broke into the computer of Tsutomu
Shimomura, a computer
security expert.

managed to get access to a set of utility
programs, that would basically give him the
tools necessary to break
in almost anywhere.

may have distributed these tools to other

The Downside!!

Kevin served five years in a Federal
correctional institution before being
released in January 2000.

Now charges $15,000 for a one hour
talk !!

Security Highlighted

Kevin Mitnick

FBI arrested Kevin in February 1995

stealing 20,000 credit
card numbers
through the Internet

valued at over one million dollars.