COSC 472 Network Security

Transcription

1 COSC 472 Network Security Instructor: Dr. Enyue (Annie) Lu Office hours: Office room: HS114 Course information: COSC 472 Network Security Annie Lu 1

2 Course overview Chapter 1: Introduction Part I: Cryptography Chapter 2: Symmetric Encryption & Message Confidentiality Chapter 3: Public-Key Cryptography & Message Authentication Part II III: Network Security Chapter 4: key Distribution & User Authentication Chapter 5: Network Access Control and Cloud Security Chapter 6. Transport-Level Security Chapter 7. Wireless Network Security Chapter 8: Security Chapter 9: IP Security Part III: System security Chapter 10. Malicious Software Chapter 11. Intruder Chapter 12. Firewalls COSC 472 Network Security Annie Lu 2

3 Chapter I: Introduction Outline What s network security Security threats Security architecture Security attacks Security services Security mechanisms Network security models COSC 472 Network Security Annie Lu 3

4 Chapter 1 Introduction The art of war teaches us to rely not on the likelihood of the enemy's not coming, but on our own readiness to receive him; not on the chance of his not attacking, but rather on the fact that we have made our position unassailable. The Art of War, Sun Tzu COSC 472 Network Security Annie Lu

5 Background Information Security requirements have changed in recent times Traditionally provided by physical and administrative mechanisms Computer use requires automated tools to protect files and other stored information Use of networks and communications links requires measures to protect data during transmission COSC 472 Network Security Annie Lu

6 Security Information Security: is about how to prevent attacks, or failing that, to detect attacks on information-based systems Computer Security: generic name for the collection of tools designed to protect data and to thwart hackers Network Security: measures to protect data during their transmission Internet Security: measures to protect data during their transmission over a collection of interconnected networks COSC 472 Network Security Annie Lu 6

7 Computer Security the protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability and confidentiality of information system resources (includes hardware, software, firmware, information/data, and telecommunications) COSC 472 Network Security Annie Lu

8 CIA Triad Data and services COSC 472 Network Security Annie Lu

9 CIA Triad Confidentiality: Data confidentiality: confidential information should not be accessible to unauthorized users Privacy: individuals control what information related to them Integrity: Data integrity: data may only be modified through an authorized mechanism System integrity: system performs intended function Availability: authorized users should be able to access data for legitimate purposes as necessary COSC 472 Network Security Annie Lu

10 Examples of Security Requirements confidentiality student grades integrity patient information availability authentication service COSC 472 Network Security Annie Lu

11 Levels of Impact can define 3 levels of impact from a security breach Low Moderate High P22: Problem1.4 COSC 472 Network Security Annie Lu

12 Computer Security Challenges 1. not simple 2. must consider potential attacks 3. procedures used counter-intuitive 4. involve algorithms and secret info 5. must decide where to deploy mechanisms 6. battle of wits between attacker / admin 7. not perceived on benefit until fails 8. requires regular monitoring 9. too often an after-thought 10. regarded as impediment to using system COSC 472 Network Security Annie Lu

13 Computer Security vs. Network Security Computer security deals with protecting a single machine Network security deals with protecting the communication and all participants in it Goal of networking is to enable communication at all times and in all scenarios! COSC 472 Network Security Annie Lu 13

14 What Does Network Security Mean? I want to talk to Alice. No one should be able to: Break into my computer Attack my computer Steal my information Use my computer to attack others Damage my computer or data Pretend to be Alice or myself or our computers Use my resources Prevent me from communicating with Alice COSC 472 Network Security Annie Lu 14

15 Aim of Course our focus is on Internet Security which consists of measures to deter, prevent, detect, and correct security violations that involve the transmission & storage of information COSC 472 Network Security Annie Lu 15

16 Security Trends COSC 472 Network Security Annie Lu 17

17 Threats and Attacks Threat: a potential for violation of security; a possible danger that might exploit a vulnerability Attack: an assault on system security that derives from an intelligent threat COSC 472 Network Security Annie Lu 18

18 What Are the Threats? No one should be able to break into my computer Hackers Break a password or sniff it off the network Exploit a vulnerability A vulnerability is a bug in the software that creates unexpected computer behavior when exploited, such as enabling access without login, running unauthorized code or crashing the computer. An exploit is an input to the buggy program that makes use of the existing vulnerability Use social engineering: eg. phishing Impersonate someone I trust Viruses and worms COSC 472 Network Security Annie Lu 19

19 What Are the Threats? No one should be able to attack my computer Denial-of-service attacks A DOS attack aims to disrupt a service by either exploiting a vulnerability or by sending a lot of bogus messages to a computer offering a service Viruses and some worms A virus is a self-replicating program that requires user action to activate such as clicking on , downloading an infected file or inserting an infected floppy, CD, etc.. A worm is a self-replicating program that does not require user action to activate. It propagates itself over the network, infects any vulnerable machine it finds and then spreads from it further. COSC 472 Network Security Annie Lu 20

20 What Are the Threats? No one should be able to steal my information From my computer or from communication I will use cryptography! There are many ways to break ciphers There are many ways to divulge partial information (e.g. who do you talk to) I would also like to hide who I talk to and when I will use anonymization techniques Anonymization hinders other security approaches that build models of normal traffic patterns COSC 472 Network Security Annie Lu 21

21 What Are the Threats? No one should be able to use my machine to attack others viruses Worms Denial-of-service attacks (including reflector attacks) COSC 472 Network Security Annie Lu 22

22 What Are the Threats? No one should be able to damage my computer or data I have to prevent break-ins I will also use cryptography to detect tampering I must replicate data to recover from tampering Denial-of-service attacks and worms can sometimes damage computers COSC 472 Network Security Annie Lu 23

23 What Are the Threats? No one should be able to successfully pretend to be Alice or myself or our computers I want to be sure who I am talking to (authentication and digital signatures) It is hard to impersonate a computer in two-way communication, such as TCP. But it has been done Plain IP spoofing seems extremely hard problem to solve IP spoofing means putting a fake IP address in the sender field of IP packets. COSC 472 Network Security Annie Lu 24

24 What Are the Threats? No one should be able to take up my resources with irrelevant messages Denial-of-service attacks Spam mail (takes time to read and fills space) Malicious mail (may contain a virus) Viruses and worms COSC 472 Network Security Annie Lu 25

25 What Are the Threats? No one should be able to prevent me from communicating with Alice Alice could be attacked Routers could be overloaded or tampered with DNS servers could be attacked COSC 472 Network Security Annie Lu 26

26 OSI Security Architecture ITU-T X.800 Security Architecture for OSI defines a systematic way of defining and providing security requirements for us it provides a useful, if abstract, overview of concepts we will study COSC 472 Network Security Annie Lu

27 Security Architecture Security Attack: Any action that compromises the security of information. Security Mechanism: A mechanism that is designed to detect, prevent, or recover from a security attack. Security Service: A service that enhances the security of data processing systems and information transfers. A security service makes use of one or more security mechanisms. COSC 472 Network Security Annie Lu 28

28 attack attack attack Passive attack: attempts to learn or make use of information from the system but does not affect system resource. Active attack: attempts to alter system resources or affect their operation COSC 472 Network Security Annie Lu 29

29 Passive Attacks Release of the message contents: read the contents of the message Traffic analysis: observe the pattern of the massage COSC 472 Network Security Annie Lu 30

30 Release of the message contents COSC 472 Network Security Annie Lu 31

31 Traffic analysis COSC 472 Network Security Annie Lu 32

32 Active attacks Masquerade: one entity pretends to be a different entity Replay: involves the passive capture of a data unit and its subsequent retransmission to produce an unauthorized effect Modification of message: some portion of a legitimate message is altered, or that messages are delayed or reordered. The denial of service: prevents or inhibits the normal use or management of communications facilities COSC 472 Network Security Annie Lu 33

33 Masquerade COSC 472 Network Security Annie Lu 34

34 Replay COSC 472 Network Security Annie Lu 35

35 Modification of message COSC 472 Network Security Annie Lu 36

36 The denial of service COSC 472 Network Security Annie Lu 37

37 Security Attacks attack COSC 472 Network Security Annie Lu 38

38 Security Attacks Interruption: This is an attack on availability Interception: This is an attack on confidentiality Modification: This is an attack on integrity Fabrication: This is an attack on authenticity COSC 472 Network Security Annie Lu 39

39 Security Mechanism feature designed to detect, prevent, or recover from a security attack no single mechanism that will support all services required however one particular element underlies many of the security mechanisms in use: cryptographic techniques COSC 472 Network Security Annie Lu 40

40 Security Mechanisms (X.800) (P. 15: Table 1.3) specific security mechanisms: encipherment, digital signatures, access controls, data integrity, authentication exchange, traffic padding, routing control, notarization pervasive security mechanisms: trusted functionality, security labels, event detection, security audit trails, security recovery COSC 472 Network Security Annie Lu 41

41 Security Service enhance security of data processing systems and information transfers of an organization intended to counter security attacks using one or more security mechanisms often replicates functions normally associated with physical documents which, for example, have signatures, dates; need protection from disclosure, tampering, or destruction; be notarized or witnessed; be recorded or licensed COSC 472 Network Security Annie Lu

42 Security Services X.800: a service provided by a protocol layer of communicating open systems, which ensures adequate security of the systems or of data transfers RFC 2828: a processing or communication service provided by a system to give a specific kind of protection to system resources COSC 472 Network Security Annie Lu

43 Security Services (P. 12: Table 1.2) Authentication - assurance that the communicating entity is the one claimed Access Control - prevention of the unauthorized use of a resource Data Confidentiality protection of data from unauthorized disclosure Data Integrity - assurance that data received is as sent by an authorized entity Non-Repudiation - protection against denial by one of the parties in a communication Proof that the message was sent by specific party (Nonrepudiation origin) Proof that the message was received by specific party (Nonrepudiation destination) Availability (permanence, non-erasure) Denial of Service Attacks Virus that deletes files COSC 472 Network Security Annie Lu 44

44 Model for Network Security COSC 472 Network Security Annie Lu 45

45 Model for Network Security using this model requires us to: 1. design a suitable algorithm for the security transformation 2. generate the secret information (keys) used by the algorithm 3. develop methods to distribute and share the secret information 4. specify a protocol enabling the principals to use the transformation and secret information for a security service COSC 472 Network Security Annie Lu 46

46 Model for Network Access Security COSC 472 Network Security Annie Lu 47

47 Model for Network Access Security using this model requires us to: 1. select appropriate gatekeeper functions to identify users 2. implement security controls to ensure only authorised users access designated information or resources trusted computer systems may be useful to help implement this model COSC 472 Network Security Annie Lu 48

48 Internet standards and RFCs The Internet society Internet Architecture Board (IAB) Internet Engineering Task Force (IETF) Internet Engineering Steering Group (IESG) COSC 472 Network Security Annie Lu 49

49 Internet RFC Publication Process COSC 472 Network Security Annie Lu 50

50 Summary Definitions of computer, network, internet security security concepts: confidentiality, integrity, availability Security architecture security attacks, services, mechanisms models for network (access) security COSC 472 Network Security Annie Lu