Chapter_15

Chapter_15 - Chapter 15: Security s The Security Problem s...

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15.1 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts Chapter 15: Security Chapter 15: Security The Security Problem Program Threats System and Network Threats Cryptography as a Security Tool User Authentication Implementing Security Defenses Firewalling to Protect Systems and Networks Computer-Security Classifications
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15.2 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts Objectives Objectives To discuss security threats and attacks To explain the fundamentals of encryption, authentication, and hashing To examine the uses of cryptography in computing To describe the various countermeasures to security attacks
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15.3 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts The Security Problem The Security Problem Security must consider external environment of the system, and protect the system resources Intruders (crackers) attempt to breach security Threat is potential security violation Attack is an attempt to breach security Attack can be accidental or malicious Easier to protect against accidental than malicious misuse
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15.4 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts Security Violations Security Violations Categories of security violations Breach of confidentiality: unauthorized reading of data Breach of integrity: unauthorized modification of data Breach of availability: unauthorized destruction of data Theft of service: unauthorized use of resources. A user may install a daemon that acts as a file server. Denial of service: involves preventing legitimate use of the system. Denial-of- service attacks. Methods used for breaching security: Masquerading (breach authentication): one participant pretends to be someone else Replay attack : replay old messages Message modification : replay attack used along with message modification to escalate privileges. Man-in-the-middle attack: attacker sits in the middle of communication flow and masquerades as sender or receiver. Session hijacking: active communication session is intercepted. This may precede man-in-the-middle attack.
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15.5 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts Standard Security Attacks Standard Security Attacks
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15.6 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts Security Measure Levels Security Measure Levels Security must occur at four levels to be effective: Physical: sites containing the computer systems must be physically secured Human: authorizing users must be done carefully Avoid social engineering Phishing: a legitimate looking email or web page misleads a user to enter confidential information Dumpster diving: attempting to gather information from trash, phonebooks, finding notes containing passwords, etc. to gain unauthorized access to computer Operating System: The system must protect itself from accidental or intentional security breaches. Should handle problems such as runaway processes, stack overflow, etc.
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Chapter_15 - Chapter 15: Security s The Security Problem s...

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