Computer Security CE408 An Overview Muhammad Najmul Islam

Computer Security (CE-408) An Overview Muhammad Najmul Islam Farooqui Assistant Professor Department of Computer Engineering 1

Course Tutors Muhammad Najmul Islam Farooqui (B) Ms. Roohi Kamal(A) Mr. Muhammad Naseem (C) Mr. Hisham Naeem (DE) Mr. Noman Ali Khan (F) 2

Time Distribution 3/4 Theory Theoretical aspects of the course 1/4 Practical Labs Mid Term Exam Practical approach to the course Labs 3

Performance Assessment Criteria Marks Distribution Total 100 points 80 20 Lectures 5 Labs 75 Course Work 2 Assign. 3 Quizzes 14 Exams 15 Mid Term Weekly Labs 6 Attendance 60 Final Lab 1, Lab 2 ……Lab n 4

Pre-Mid Term Course Coverage 5

Week 1. 2. 3. 4. 5. 6. 7. 8. Topics Covered Introduction, General discussion about course contents, Historical Review of Computer Security, Threats and attacks to Data Security, A Generic Model of Network Security What is Cryptography & Cryptanalysis, Concepts of Cryptographic Algorithm, Conventional Cryptographic techniques, Substitution and Transposition, Cryptanalysis Techniques Introduction to S-DES, Overview and Mechanism of Encryption in DES, DES Design Principles Triple Data Encryption Standard (3 -DES), Modes of Operations of Symmetric Key Algorithms, International Data Encryption Algorithm (IDEA) Study Ref. Pg # 31 -54 Pg # 55 -89 Pg # 90 -124 Pg # 217 -241, IDEA Handout Raijndael Algorithm (The Finalist of AES), Simplified AES, Mechanism of Encryption in AES Pg # 171 -214 Key Exchange Problem, Key Exchange Approaches using Symmetric Key algorithm and Need for Public Key Cryptography Pg # 435 - 453 Number Theory, Modular Arithmetic, Euler’s Function and Public Key Cryptography, Diffie-Hellman Key Exchange Algorithm Pg # 267 -275, 324332 Introduction to RSA, Key Generation and Encryption, Examples, RSA Applications in Network Security Pg # 290 -331 6

Post-Mid Term Course Coverage 7

9. 10. Authentication Functions, Hash Function and its properties, Secure Hashing Algorithm (SHA), Digital Signature and Authentication Requirements, Message Authentication Code, Introduction to Digital Signatures, RSA Approach, Digital Signature Standard (DSS) and its proof Pg #351 -376, 386 -399 Pg # 419 -430 11. Email Security Standards, PGP Certificate and Algorithms, Introduction to Trust Models Pg # 591 - 599, 636 -638 12. Introduction to IPSec, IPSec Security Model, IPSec modes and protocols, IPSec Technologies Pg # 639 -662 13. 14. Introduction to VPNs, VPN Features, Protocols used in VPNs, L 2 TP, PPTP Introduction & History of SSL, SSL in Client-Server Architecture, Transport Layer Security Introduction to Firewalls, Components of Firewalls, Types of Firewalls, 15. 16. Architecture and Policies in Intrusion Detection Systems, Introduction to Viruses, and Trojans Final Examination Lecture Notes Pg # 509 -543 Lecture Notes, Online Chapter 8

Reading Resources Text Book Reference Books ◦ Specific to the course ◦ General to the topic Internet Sources 9

Text Book Cryptography and Network Security: Principles & Practice (Fifth Edition) ◦ By William Stallings – Prentice Hall Publication 10

Reference Books Specific to the Course ◦ Handbook of Cryptography By Alfred J. Menezese, Paul C. van Orchi ◦ Network Security Essentials, 2 nd Edition William Stallings, Prentice Hall, 2003 ◦ Web Security: A step-by-step Reference Guide By Lincoln D. Stein – Addison Wesley Publication ◦ Internet Security Protocols: Protecting IP Traffic (Low Price Edition) By Uyless Black – Pearson Education Asia Publication General to the Topic ◦ Active Defense: A Comprehensive Guide to Network Security By Chris Brenton & Cameron Hunt 11

Internet Sources http: //www. ssuet. edu. pk/~mfarooqui http: //sites. google. com/site/ibrahimmhr http: //www. dcs. ed. ac. uk/home/compsec/ http: //www. infosecuritymag. com/ http: //www. w 3. org/Security/Faq/ http: //www. iwar. org. uk/comsec/resources/ security-lecture/ 12

How to get what we discuss? Online Access http: //www. ssuet. edu. pk/courses/ce 408/Comp. Sec/ Soft Copy http: //www. ssuet. edu. pk/courses/ce 408/Comp. Sec/ Hard Copy Will not be provided 13

Codes of Conduct Strictly practice your attendance in the class and labs. No relaxation, compensation or adjustment in your attendance. Be in Uniform (at least in the class) Preserve the sanity of the class, teachers, department and the University. Help us in serving you for a better future. 14

What is 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) is called Computer Security. 15

Computer Security Computer security is a heady concoction of science, technology, and engineering. A secure system is only as strong as the weakest link, so each part of the mix needs to be good. 16

Definitions Security ◦ The protection of assets. Computer Security ◦ Focuses on protecting assets within computer systems. Just as real-world physical security systems vary in their security provision (e. g. , a building may be secure against certain kinds of attack, but not all), so computer security systems provide different kinds and amounts of security. 17

What is Computer Security? For some Computer Security is controlling access to hardware, software and data of a computerized system. � A large measure of computer security is simply keeping the computer system's information secure. � In broader terms, computer security can be thought of as the protection of the computer and its resources against accidental or intentional disclosure of confidential data, unlawful modification of data or programs, the destruction of data, software or hardware. � Computer security also includes the denial of use of one’s computer facilities for criminal activities including computer related fraud and blackmail. � Finally, computer security involves the elimination of weaknesses or vulnerabilities that might be exploited to cause loss or harm. � 18

The Need for Computer Security Why the need for Computer Security? ◦ The value of computer assets and services What is the new IT environment? ◦ Networks and distributed applications/services ◦ Electronic Commerce (E-commerce, E-business) 19

The Value of Computer Assets and Services � Most companies use electronic information extensively to support their daily business processes. � Data is stored on customers, products, contracts, financial results, accounting etc. � If this electronic information were to become available to competitors or to become corrupted, false or disappear, what would happen? What would the consequences be? Could the business still function? 20

Network Security Issues � “The network is the computer” � Proliferation of networks has increased security risks much more. � Sharing of resources increases complexity of system. � Unknown perimeter (linked networks), unknown path. � Many points of attack. � Computer security has to find answers to network security problems. � Hence today the field is called Computer and Network Security. 21

Security Trends 22

Is there a Security Problem in Computing? � Computer fraud in the U. S. alone exceeds $3 billion each year. � Less than 1% of all computer fraud cases are detected over 90% of all computer crime goes unreported. � “Although no one is sure how much is lost to EFT crime annually, the consensus is that the losses run in the billions of dollars. Yet few in the financial community are paying any heed. ” � Average computer bank theft amounts to $1. 5 million. 23

Computer Security Losses 24

Security Technologies Used 25

Natural Disasters – Another Dimension � Millions of dollars of damage resulted from the 1989 San Francisco earthquake. � The fire at Subang International Airport knocked out the computers controlling the flight display system. A post office near the Computer Room was also affected by the soot which decommissioned the post office counter terminals. According to the caretaker, the computers were not burnt but crashed because soot entered the hard disks. � Fire, Earthquakes, Floods, Electrical hazards, etc. � How to prevent? 26

Computer Security Requirements Secrecy Integrity Availability Authenticity Non-repudiation Access control 27

Secrecy (Confidentiality) Secrecy requires that the information in a computer system only be accessible for reading by authorized parties. This type of access includes: ◦ Printing ◦ Displaying ◦ Other forms of disclosure, including simply revealing the existing of an object 28

Integrity requires that the computer system asset can be modified only by authorized parties. Modification includes: ◦ ◦ ◦ Writing Changing status Deleting and Creating 29

Availability requires that computer system assets are available to authorized parties. Availability is a requirement intended to assure that systems work promptly and service is not denied to authorized users. 30

More About Integrity � Integrity: In lay usage, information has integrity when it is timely, accurate, complete, and consistent. However, computers are unable to provide or protect all of these qualities. Therefore, in the computer security field, integrity is often discussed more narrowly as having two data integrity and system integrity. � “Data integrity is a requirement that information and programs are changed only in a specified and authorized manner. ” � System integrity is a requirement that a system “performs its intended function in an unimpaired manner, free from deliberate or inadvertent unauthorized manipulation of the system. ” � The definition of integrity has been, and continues to be, the subject of much debate among computer security experts. 31

Security of Data Confidentiality Data Integrity Data Availability Data Secure Data 32

Authenticity Authenticity means that parties in a information services can ascertain the identity of parties trying to access information services. Also means that the origin of the message is certain. Therefore two types: ◦ Principal Authentication ◦ Message Authentication 33

Non-repudiation Originator of communications can’t deny it later. Without non-repudiation you could place an order for 1 million dollars of equipment online and then simply deny it later. Or you could send an email inviting a friend to the dinner and then disclaim it later. Non-repudiation associates the identity of the originator with the transaction in a nondeniable way. 34

Access Control Unauthorized users are kept out of the system. Unauthorized users are kept out of places on the system/disk. Typically makes use of Directories or Access Control Lists (ACLs) or Access Control Matrix Objects: Resources that need to be protected Subjects: Entities that need access to resources Rights: Permissions Each entry is a triple <subject, object, rights> 35

Access Control Matrix OBJECT 1 OBJECT 2 OBJECT 3 OBJECT 4 SUBJECT 1 RW RW R X SUBJECT 2 R RW R R SUBJECT 3 X X RW RW SUBJECT 4 R RW SUBJECT N X R R X 36

Security Requirements are often Combined For example: User authentication used for access authorization control purposes in confidentiality. Non-repudiation is combined with authentication. Confidentiality Integrity Availability 37

Type of Attacks/Threats in Computer Systems A threat is a danger which could affect the security (confidentiality, integrity, availability) of assets, leading to a potential loss or damage. Interruption Interception Modification Fabrication 38

Type of Attacks in Computer Systems 39

Normal Flow of Information 40

Interruption �An asset of the system is destroyed or becomes unavailable or unusable. This is an attack on the availability. �Examples include destruction of a piece of hardware, such as a hard disk, the cutting of a communication link, or the disabling of the file management system. �DOS - Denial of Service Attacks have become very well known. 41

Interruption 42

Interception Information disclosure/information leakage An unauthorized party gains access to an asset. This is an attack on confidentiality. The unauthorized party could be a person, a program, or a computer. Examples include: ◦ wiretapping to capture data in a network ◦ the illicit copying of files or programs 43

Interception 44

Modification is integrity violation. An unauthorized party not only gains access to but tampers with an asset. This is an attack on the integrity. Examples include changing values in a data file, altering a program so that it performs differently, and modifying the content of a message being transmitted in a network. 45

Modification 46

Fabrication An unauthorized party inserts counterfeit objects into the system. This is an attack on the authenticity. Examples include the insertion of spurious messages in a network or the addition of records to a file. 47

Fabrication 48

Classification of Attacks Computer Security attacks can be classified into two broad categories: ◦ Passive Attacks can only observe communications or data. ◦ Active Attacks can actively modify communications or data. Often difficult to perform, but very powerful. Examples include Mail forgery/modification TCP/IP spoofing/session hijacking 49

Passive Attacks and Active Attacks 50

Passive Attacks and Active Attacks 51

Passive Attacks Eavesdropping on or monitoring of transmission. The goal of the opponent is to obtain information that is being transmitted. Two types: ◦ Release-of-message contents ◦ Traffic Analysis 52

Release-of-message Contents Opponent finds out the contents or the actual messages being transmitted. How to protect? ◦ Encryption ◦ Steganography 53

Traffic Analysis More subtle than release-of-message contents. Messages may be kept secret by masking or encryption but … The opponent figures out information being carried by the messages based on the frequency and timings of the message. How to protect? ◦ Data/Message Padding ◦ Filler Sequences 54

Passive Attacks Problems Difficult to detect because there is no modification of data. Protection approach should be based on prevention rather than detection. 55

Active Attacks Active attacks involve some sort of modification of the data stream or the creation of a false stream. Four sub-categories: ◦ ◦ Masquerade Replay Modification of Messages Denial of service 56

Masquerade An entity pretends to be another. For the purpose of doing some other form of attack. Example a system claims its IP address to be what it is not, IP spoofing. How to protect? ◦ Principal/Entity Authentication 57

Replay First passive capture of data and then its retransmission to produce an unauthorized effect. Could be disastrous in case of critical messages such as authentication sequences, even if the password were encrypted. How to protect? ◦ Time stamps ◦ Sequence Numbers 58

Modification of Messages Some portion of a legitimate message is altered or messages are delayed or reordered to produce an unauthorized effect. How to protect? ◦ Message Authentication Codes ◦ Chaining 59

Denial of Service - DOS Prevents the normal use or management of communication facilities. Such attacks have become very common on the Internet especially against web servers. On the Internet remotely located hackers can crash the TCP/IP software by exploiting known vulnerabilities in various implementations. One has to constantly look out for software updates and security patches to protect against these attacks. 60

Problems with Active Attacks Easy to detect but difficult to prevent. Efforts are directed to quickly recover from disruption or delays. Good thing is that detection will have a deterrent effect. 61

How Threats Affect Computer Systems Interruption (Denial of Service) Interception (Theft) HARDWARE Interruption (Deletion) Modification (Malicious Code) Interruption (Loss) Modification Interception (Theft) SOFTWARE DATA Interception (Eavesdropping) Fabrication 62

A Model for Network Security 63

Security Protocols �A protocol is a series of steps, involving two or more parties, designed to accomplish a task. ◦ Every one involved in a protocol must know the protocol and all of the steps to follow in advance. ◦ Everyone involved in the protocols must agree to follow it. ◦ The protocol must be unambiguous; each step must be well defined and there must be no chance of misunderstanding. ◦ The protocol must be complete; there must be a specified action for every possible situation. ◦ It should not be possible to do more or learn more than what is specified in the protocol. 64

The Actors in Security Protocols � Alice First participant in all the protocols � Bob Second participant in all the protocols � Carol Participant in three- and four-party protocols � Dave Participant in four-party protocols � Eve Eavesdropper � Mallory Malicious active intruder � Trent Trusted arbitrator � Victor Verifier � Peggy Prover � Walter Warden; he’ll be guarding Alice and Bob in some protocols 65

Security Protocol Types � Arbitrated Protocols � Adjudicated Protocols � Self Enforcing Protocols � Example Protocols ◦ Key Exchange Protocols ◦ Authentication Protocols ◦ Time stamping Service ◦ Digital Cash Trent Alice Bob (a) Arbitrated Protocol Alice Bob Evidence Alice Evidence Trent (After the fact) (b) Adjudicated Protocol (c) Self-enforcing Protocol Bob 66

Security Protocol Layers §The further down you go, the more transparent it is §The further up you go, the easier it is to deploy 67

Security Services Provided by Security Protocols Access control: Protects against unauthorized use. Authentication: Provides assurance of someone's identity. Confidentiality: Protects against disclosure to unauthorized identities. Integrity: Protects from unauthorized data alteration. Non-repudiation: Protects against originator of communications later denying it. 68

Security Mechanisms Three basic building blocks are used: ◦ Encryption is used to provide confidentiality, can provide authentication and integrity protection. ◦ Digital signatures are used to provide authentication, integrity protection, and nonrepudiation. ◦ Checksums/hash algorithms are used to provide integrity protection, can provide authentication. One or more security mechanisms are combined to provide a security service/protocol. 69

Services, Mechanisms, Algorithms A typical security protocol provides one or more security services (authentication, secrecy, integrity, etc. ) Services are built from mechanisms. Mechanisms are implemented using algorithms. Services (Security Protocols) SSL Signatures DSA RSA Encryption RSA DES Hashing SHA 1 MD 5 Mechanisms Algorithms 70

Services, Mechanisms, Algorithms Security Protocols (Services) Standards-based Security Protocols SSL Proprietary Security Protocols IPSec Private. Wire Big Brother Hashing Key Exchange MD-5 SHA-1 Diffie-Hellman Mechanisms Encryption Signature Algorithms Symmetric DES Asymmetric RSA ECC Asymmetric DSA RSA Symmetric DESMAC 71

Encryption and Security Encryption is a key enabling technology to implement computer security. But Encryption is to security like bricks are to buildings. In the next module we will study encryption in detail. 72

Network Access Security Model Firewalls and Security Gateways are based on this model 73

Computer security is based on eight major elements: 1. Computer security should support the mission of the organization. 2. Computer security is an integral element of sound management. 3. Computer security should be cost-effective. 4. Computer security responsibilities and accountability should be made explicit. 5. System owners have computer security responsibilities outside their own organizations. 6. Computer security requires a comprehensive and integrated approach. 7. Computer security should be periodically reassessed. 8. Computer security is constrained by societal factors. 74

Usability and Security Determine where on this line your organization needs lie Convenience / Usability 0 Security 75

Typical Security Solutions and Technologies � Physical security � Encryption � Access control � Automatic call back � Node authentication � Differentiated access rights � Antivirus software � Public Key Infrastructure � Firewalls � User authentication � Passwords and passphrases � Challenge-response systems � Token or smart cards � Exchange of secret protocol � Personal characteristics Biometrics 76