453 Network Security

Section 1: Introduction to Network Security

Dr. E.C. Kulasekere

Sri Lanka Institute of Information Technology - 2006

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-Ousley, Keith Strassberg Tata McGraw-Hill 2004.

Cryptography and Network Security/3e William Stallings, Pearson Ed. 2003.

Syllabus 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,

Kerberos. Application Security: Electronic Commerce and

E-mail.

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 terror.

Other Information

Web site: http://www.ent.mrt.ac.lk/~ekulasek/ns

Email: ekulasek@ent.mrt.ac.lk

Telephone: 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

enter Dont talk to strangers - even if you see some

one you know Look beyond. Dont share your secrets keep sniffers at bay Dont accept gifts from strangers Play nice with others Leave your valuables at home. Dont 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

hostAre these definitions enough?

More Classifications Three Ds 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

planning 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 mechanisms.

Normal flow of Information

source destination

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.

Interception

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.

Interruption

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.

Modification

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.

Fabrication

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

concerned. 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 detected.

Examples are Eavesdropping or monitoring of traffic.

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. Masquerading The entity pretends to be a different

entity. Eg. Use a sniffer on a telnet stream Replay passive capture of data, alter and then

retransmit.

Security Services

Confidentiality (privacy) is the protection of transmitted data from passive attacks.

Authentication (who created or sent the data) is 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 Separation

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 BetweenServices 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 algorithm.

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 service.

Other Considerations Network Design Considerations

Designing for acceptable risk. Use of network models with security (LAN/WAN more

secure?, Dedicated/non-dedicated?, segregation and isolation)

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 HighlightedKevin 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

hackers.

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.