1. Lecture 1: Foundation of Network Security
NET 536 Network Security
Networks and Communication Department
Lecture 1: Foundation of Network Security

2. lecture contents: Computer Security vs Network Security
Security Attack
Passive attack Vs Active attack
Why computer and network security is important?
Network Security Services
Security Trinity
Challenges of computer and network security
Conclusion
24-Nov-18
Networks and Communication Department

3. Computer Security vs Network Security
Computer security: involves implementing measures to secure a single computer (protecting the ressources stored on that computer).
Network security: involves protecting all the ressources on a network. We must consider not only the computers on the network but other network devices and data transmitted across the network.
24-Nov-18
Networks and Communication Department

4. Security attack
Security attack is any action that comprises the security of information owned by an organization.
24-Nov-18
Networks and Communication Department

5. Passive attack Vs Active attack
Attempts to learn or make use of information from the system but does not affect system ressources.
The goal is to obtain information that is being transmitted.
Telephone converstaion, electronic message…
This type of attack is difficult to detect (it does not involve any alteration in data).
Attempts to involve some modification of the data stream or the creation of a false stream.
This type of attack is easier to detect than passive attack.
24-Nov-18
Networks and Communication Department

6. Why computer and network security is important?
Protect company assests (hardware and software).
Gain competive advantage: developping and maintaing effective security measures can provide an organization with a competive advantage over its competion.
Keep your job: to secure one’s position within an organization and to ensure futur career, it is important to put into place measures that protect organizational assests.
24-Nov-18
Networks and Communication Department

7. Network Security Services
Network security: can provide one of the five services: confidentiality, integrity, authentification, nonrepudation, and avaialability.
Confidentiality/privacy:
the transmitted message must make sense to only the intended receiver. To the others, the message must be garbage. When a costumer communicates with her bank, she expects that her communication is totaly confidential.
24-Nov-18
Networks and Communication Department

8. Network Security Services
2. Integrity:
the data must arrive to the receiver exactly as they were sent.
for example: A request for transferring 100$ should not be changed to a request for 1000$.
3. Authentification:
the receiver needs to be sure of the sender’s identity.
4.Nonrepudation :
a sender must not be able to deny sending a message that he or she , in fact, did send.
5. Avialability:
availability to be the property of a system or a system resource being accessible and usable upon demand by an authorized system entity, according to performance specifications for the system.
For example: a system is available if it provides services according to the system design whenever users request them
24-Nov-18
Networks and Communication Department

9. Security Trinity
Network security is based on: prevention, detection, and response.
Security trinity should be the foundation for all security policies.
Security
Detection
Response
Prevention
24-Nov-18
Networks and Communication Department

10. Security Trinity
Prevention: in developping network security schemes, any organization should emphasize preventive measures over detection and response. It is more efficient and much more cost effective to prevent a security attack than to detect or repond to one.
-Detection: once the preventive measures fail, procedures need to be put in place to detect immediatly to detect the araised attack.
-Response: we need to develop a plan that identifies the appropriate response to a security atatck (who is responsable to execute some actions, what is the appropriate action ?)
24-Nov-18
Networks and Communication Department

11. Challenges of computer and network security
Security is not simple as it might first appear to the novice: we need to consider potential attacks . Security mechanisms typically involve more than a paticular algorithm.
Having designed various security mechanisms, it is necessary to decide where to use them (physical and logical sense). What points in a network are certain secured mechanisms needed? What layer or layers of our architecture should mechanisms be placed?
24-Nov-18
Networks and Communication Department

12. Conclusion
◆ The Open Systems Interconnection (OSI) security architecture provides a systematic framework for defining security attacks, mechanisms, and services. ◆ Security attacks are classified as either passive attacks, which include unauthorized reading of a message of file and traffic analysis or active attacks, such as modification of messages or files, and denial of service. ◆ A security mechanism is any process (or a device incorporating such a process) that is designed to detect, prevent, or recover from a security attack. Examples of mechanisms are encryption algorithms, digital signatures, and authentication protocols. ◆ Security services include authentication, access control, data confidentiality,data integrity, nonrepudiation, and availability.
24-Nov-18
Networks and Communication Department

13. References
William Stallings, ”Cryptography and Network Security”, Prentice Hall, 5th edition ( chapter #1 )
24-Nov-18
Networks and Communication Department