453 Network Security453 Network Security

Section 1: Introduction to Network Security

Dr. E.C. Kulasekere

Sri Lanka Institute of Information Technology - 2006

Text BooksText 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.

SyllabusSyllabus• 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 …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 InformationOther 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 StudentsExpectation 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 SectionOutline 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?Security is it a New Concept?• Lock the Doors and Windows. Control access• Role Based Access - Only Mom is allowed to enter• Don’t talk to strangers - even if you see some one

you know Look beyond.• Don’t share your secrets – keep sniffers at bay• Don’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 SecurityLevels 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 host

Are these definitions enough?

More ClassificationsMore 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 planning– Customer confidence

Attack, Services and MechanismsAttack, 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 AttacksSecurity Attacks

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 …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 …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 …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 TypesAttack 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 AttackPassive 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 AttackActive 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 ServicesSecurity 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 MechanismsSecurity 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

Relationship BetweenServices and Mechanisms

A Model for Network SecurityA Model for Network Security

Design Issues in the ModelDesign 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 ConsiderationsOther 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

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!!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 MitnickSecurity Highlighted - Kevin Mitnick

– FBI arrested Kevin in February 1995 • stealing 20,000 credit-card numbers through the Internet

• valued at over one million dollars.