1. 14.1 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Protection

2. 14.2 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Goals of Protection Operating system consists of a collection of objects, hardware or software Each object has a unique name and can be accessed through a well-defined set of operations Protection problem - ensure that each object is accessed correctly and only by those processes that are allowed to do so

3. 14.3 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Principles of Protection Guiding principle – principle of least privilege Programs, users and systems should be given just enough privileges to perform their tasks

4. 14.4 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Domain Structure Access-right = where rights-set is a subset of all valid operations that can be performed on the object. Domain = set of access-rights

5. 14.5 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Access Matrix View protection as a matrix (access matrix) Rows represent domains Columns represent objects Access(i, j) is the set of operations that a process executing in Domain i can invoke on Object j

6. 14.6 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Access Matrix

7. 14.7 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Use of Access Matrix (Cont) Access matrix design separates mechanism from policy Mechanism  Operating system provides access-matrix + rules  If ensures that the matrix is only manipulated by authorized agents and that rules are strictly enforced Policy  User dictates policy  Who can access what object and in what mode

8. 14.8 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Access Matrix of Figure A With Domains as Objects Figure B

9. 14.9 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Access Control Protection can be applied to non-file resources Solaris 10 provides role-based access control (RBAC) to implement least privilege Privilege is right to execute system call or use an option within a system call Can be assigned to processes Users assigned roles granting access to privileges and programs

10. 14.10 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Role-based Access Control in Solaris 10

11. 14.11 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Security

12. 14.12 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition The Security Problem Security must consider external environment of the system, and protect the system resources Threat is potential security violation Attack is attempt to breach security Attack can be accidental or malicious Easier to protect against accidental than malicious misuse

13. 14.13 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Security Violations Categories Breach of confidentiality Breach of integrity Breach of availability Theft of service Denial of service Methods Masquerading (breach authentication) Replay attack  Message modification Man-in-the-middle attack Session hijacking

14. 14.14 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Standard Security Attacks

15. 14.15 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Security Measure Levels Security must occur at four levels to be effective: Physical Human  Avoid social engineering, phishing Operating System Network Security is as weak as the weakest link in the chain

16. 14.16 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Program Threats Trojan Horse Code segment that misuses its environment Exploits mechanisms for allowing programs written by users to be executed by other users Spyware: software that enables a user to obtain covert information about another's computer activities by transmitting data covertly from their hard drive., pop-up browser windows Trap Door Specific user identifier or password that circumvents normal security procedures Could be included in a compiler

17. 14.17 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Program Threats Logic Bomb Logic bombs are small programs or sections of a program triggered by some event such as a certain date or time, a certain percentage of disk space filled, the removal of a file, and so on. For example, a programmer could establish a logic bomb to delete critical sections of code if she is terminated from the company. Logic bombs are most commonly installed by insiders with access to the system. Stack and Buffer Overflow Exploits a bug in a program (overflow either the stack or memory buffers)

18. 14.18 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition Program Threats (Cont.) Many categories of viruses, many thousands of viruses Boot sector virus Source code virus Polymorphic virus Encrypted virus Stealth: A stealth virus is complex malware that hides itself after infecting a computer. Once hidden, it copies information from uninfected data onto itself and relays this to antivirus software during a scan. This makes it a difficult type of virus to detect and delete. Multipartite: » A multipartite virus uses multiple infection methods, typically infecting both files and boot sectors. Accordingly, multipartite viruses combine the characteristics of file infector and boot sector viruses. Examples of multipartite viruses include Flip and Invader.infectioninfectingfilesboot sectorsfile infectorboot sector virusesFlipInvader

19. 14.19 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition A Boot-sector Computer Virus

20. 14.20 Silberschatz, Galvin and Gagne ©2009 Operating System Concepts with Java – 8 th Edition End