Download
1 / 42
420 likes | 553 Views
Mehrdad Nourani. Network Security. Network Security Essentials. Session 02. Security Issues: Past & Present. Security in Early Days. In the early days of data processing, the security of information was provided primarily by physical and administrative means:
E N D
Mehrdad Nourani Network Security
Network Security Essentials Session 02
Security in Early Days • In the early days of data processing, the security of information was provided primarily by physical and administrative means: • Computer buildings, floors, rooms were guarded and alarmed to prevent outsides from intruding and disrupting operations. • The focus was on physical break-ins, the theft of computer equipment, and the physical theft or destruction of disk packs, tape reels, punch cards, or other media. • Insiders were kept at bay and access was limited to a small set of computer professionals.
Information Security • The requirements of information security within organizations have undergone two major changes: • The introduction of shared systems such as time-shared and/or systems that can be accessed over the public telephone or data network. • The introduction of distributed systems and the use of networks and communications facilities for carrying data between terminal user and computer and between computer and computer.
Computer vs. Network Security • Computer security is the generic term for a collection of tools designed to protect data and to thwart hackers. • Network security is the security measures that are needed to protect data during their transmission. • In most systems, the boundaries between computer security and network security are blurred since most, if not all, of today’s systems are distributed in nature. • Networking is a core part of today’s environment.
Examples of Security Violations • User A transmits a sensitive file to user B; User C intercepts the file and captures a part or all of it. • An employee is fired without warning. The personnel manager sends a message to invalidate the employee’s account. The employee intercepts the message and then retrieves some sensitive information. • A message is sent from a customer to a stockbroker with instructions for a transaction; the investment loses value and the customer denies sending the message. • …
Different Aspects of Security • Security attack: Any action that compromises the security of information owned by an organization. • 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 the data processing systems and the information transfers of an organization. • A system designed to counter security attacks.
Reasons for Cheating (1) • 1. Gain unauthorized access to information. • 2. Impersonate another user to shift responsibility or else to use the other’s license for the purpose of: • a. Originating fraudulent information • b. Modifying legitimate information • c. Using fraudulent identity to gain unauthorized access • d. Fraudulently authorizing transactions or endorsing them • 3. Disavow responsibility or liability for information the cheater did originate • 4. Claim to have received from some other user information that the cheater created (i.e., fraudulent attribution of responsibility or liability).
Reasons for Cheating (2) • 5. Claim to have sent to a receiver (at a specified time) information that was not sent (or was sent at a different time) • 6. Either disavow receipt of information that was in fact received, or claim a false time of receipt. • 7. Enlarge cheater’s legitimate license (for access, origination, distribution, etc.) • 8. Modify (without authority to do so) the license of others (fraudulently enroll others, restrict, or enlarge existing licenses, etc.)
Reasons for Cheating (3) • 9. Conceal the presence of some information (a covert communication) in other information (the overt communication) • 10. Insert self into a communication link between other users as an active (undetected) relay point. • 11. Learn who accesses which information (sources, files, etc.) and when the accesses are made even if the information itself remains concealed (e.g., a generalization of traffic analysis from communications channels to databases, software, etc.)
Reasons for Cheating (4) • 12. Impeach an information integrity protocol by revealing information the cheater is supposed to (by terms of the protocol) keep secret • 13. Pervert the function software, typically by adding a covert function • 14. Cause others to violate a protocol by means of introducing incorrect information • 15. Undermine confidence in a protocol by causing apparent failures in the system • 16. Prevent communication among other users, in particular, surreptitious interference to cause authentic communication to be rejected as unauthentic
Internet Security • Our focus is on Internet Security • It consists of measures to deter, prevent, detect, and correct security violations that involve the transmission of information • We need systematic way to define requirements • Consider three aspects of information security: • security attack • security mechanism • security service
Security Attack • Any action that compromises the security of information owned by an organization • Information security is about how to prevent attacks, or failing that, to detect attacks on information-based systems • Should include a wide range of attacks • Can focus of generic types of attacks • Note: often threat & attack mean same
Categories of Security Attacks • Interruption • Attack on availability • Interception • Attack on confidentiality • Modification • Attack on integrity • Fabrication • Attack on authenticity
Information Source Information Destination Normal Flow • Normal Flow is the flow of information from an information source, such as a file, or a region of main memory, to a destination, such as another file or user.
Information Source Information Destination Interruption • An asset of the system is destroyed or becomes unavailable or unusable. • This is an attack on availability. • Examples: The destruction of hardware, the cutting of a communication line, or the disabling of the file management system.
Information Source Information Destination Unauthorized Party Interception • 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: Wiretapping to capture data in a network and the unauthorized copying of files or programs.
Information Source Information Destination Unauthorized Party Modification • An authorized party not only gains access to but tampers with an asset. • This is an attack on integrity. • Examples: Changing values in a data file, altering a program so that it performs differently, or modifying the content of messages being transmitted in a network.
Information Source Information Destination Unauthorized Party Fabrication • An authorized party inserts counterfeit objects into the system. • This is an attack on authenticity. • Examples: The insertion of spurious (fake) messages in a network or the addition of records to a file.
Passive Attacks • Passive attacks eavesdrop or monitor the transmission. • Goal: To obtain transmitted information • Two types of passive attacks: • 1. Release of contents: A telephone conversation, an electronic mail message, or confidential information. • 2. Traffic analysis: Using the location and identities of hosts and the frequency and length of messages to determine the type of communication taking place. • Passive attacks are difficult to detect since they do not involve any alteration of data. • The emphasis is on prevention rather than detection.
Active Attacks • Active attacks may modify of the data stream or create a false stream. • Four Types of active attacks: • 1. Masquerade: takes place when one entity pretends to be a different entity. This form usually includes one of the other forms of active attack. • 2. Replay: involves the passive capture of a data unit and its subsequent retransmission to produce an unauthorized effect. • 3. Modification: occurs when an unauthorized party gains access to and tampers with an asset. This is an attack on integrity. • 4. Denial of service: prevents or inhibits the normal use or management of communications facilities.
Method and Procedure • A mechanism that is designed to detect, prevent, or recover from a security attack • No single mechanism that will support all functions required • However, one particular element underlies many of the security mechanisms in use: cryptographic techniques • Hence, we will cover this area
Mechanisms Explain Details • specific security mechanisms: • 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
Importance of Security Service • Is something that enhances the security of the data processing systems and the information transfers of an organization • Intended to counter security attacks • Makes use of one or more security mechanisms to provide the service • Replicates functions normally associated with physical documents • E.g. have signatures, dates; need protection from disclosure, tampering, or destruction; be notarized or witnessed; be recorded or licensed
Security Services • Confidentiality is the protection of transmitted data from passive attacks. • Authentication is concerned with assuring that a communication is authentic. • Integrity assures that messages are received as sent. • A connection-oriented integrity service should assure that there are no duplicates, insertions, deletions, modifications, reordering, or replays. • A connectionless integrity service deals only with an individual message.
Security Services (cont.) • Non-Repudiation prevents either the sender or receiver from denying a transmitted message. • Access Control is the ability to limit and control the access to host systems and applications via communications links. • Availability is the ability to prevent the loss or a reduction in availability of elements of a distributed system.
Requirement of the Security Model • Design a suitable algorithm for the security transformation • Generate the secret information (keys) used by the algorithm • Develop methods to distribute and share the secret information • Specify a protocol enabling the principals to use the transformation and secret information for a security service
Operation of the Model • A message is presented to be transferred from one party to another across some sort of internet. • The two parties (principals) in the transaction must cooperate for the exchange to take place. • A logical information channel is established by defining a route through the internet from source to destination using a communications protocol such as TCP/IP.
Components of the Model • Security is an issue when it is necessary to protect the transmission from an opponent. • All techniques for providing security have two components: • 1. A security-related transformation on the information to be sent • 2. Some secret information share by the two principles and hopefully unknown to opponent. • Additionally, in some cases a trusted third party may be used for distributing the secret information or arbitrating disputes between the two parties over authenticity.
Requirement of the Security Model • Select appropriate gatekeeper functions to identify users • Implement security controls to ensure only authorised users access designated information or resources • Trusted computer systems can be used to implement this model
Internet Standards • Internet Society is responsible for the development and publication of standards for use over the Internet. • Internet Society is a professional membership organization. • Internet Society is involved in Internet development and standardization. • Internet Society is the coordinating committee for Internet design, engineering, and management.
Organizations to Review Standards • Internet Society consists of three organizations: • 1. Internet Architecture Board (IAB) which is responsible for defining the overall architecture of the Internet. • 2. Internet Engineering Task Force (IETF) which is the protocol development arm of the Internet. • 3. Internet Engineering Steering Group (ISEG) which is responsible for technical management of OETF activities and the Internet standard process.
Request For Comments (RFC) • RFCs are the Internet Standards • RFC is developed and published by the Internet Engineering Task Force (IETF) • Approved by the Internet Engineering Steering Group (IESEG). • To become a standard, the RFC must … • Be stable and well-understood • Be technically competent • Have multiple, independent, and interoperable implementations with substantial operational experience. • Enjoy significant public support • Be recognizably useful in some or all parts of the Internet
