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Operating System: Presented To: Sir. Ahsan Raza Presented By: Shaista Sumreen (06-04) Aliya Zafar (06-06) Mamoona Sadia (06-08) Javaria Qayyum (06-26) Sana Tareen (06-31) Sadia Riaz (06-33)

bzupages.com Services of Operating System: Process Management Multi-Tasking Interrupt Processing Memory Management Registers Random Access Memory Disk Storage Disk & File System Networking Security

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Outline Operating System Security Protection Mechanism H/W Security Protection of Memory Access Control Mechanism Auditing Fault Tolerance Summary

bzupages.com Shaista Sumreen Topic Protection Mechanism H/W Security

bzupages.com Protection Mechanism:(1) Operating system security is provided by gates that users must pass through before entering the operating system environment, and permission matrixes that determine what they are able to do once inside.

bzupages.com Protection Mechanism:(2) Dialup gate Login gate Root gate Secure RPC gate File and directory matrix NIS+ objects matrix

bzupages.com Protection Mechanism: O.S provides protection with following Spectrum: No protection Isolation Share all Or Share nothing Share via access limitation Share via dynamic capabilities Limited use of an object

bzupages.com Hardware Security:(1) Problem??? Examples: Telephone SIM cards Smart cards (used for access, TV decoders, ID, money...) Public ATM machines

bzupages.com Hardware Security:(2) Install a version of the PROM monitor that either does not provide (or at least password protects) the commands to examine and change memory contents. Ensure that workstations cannot be taken into single-user mode without providing the "root" (or a PROM monitor "hardware") password.

bzupages.com Protecting data from hardware failures:(3) Use Backups. Use Redundant Arrays of Inexpensive Disks (RAID). Failure of a single disk should not cause any data loss. Beware of manufacturers.

bzupages.com Protection Of Memory: Memory Encryption Control Unit (MECU) encrypts all memory transfers between the level 2 cache and main memory. The keys used to encrypt memory blocks are derived from secret information present on removable authentication tokens, e.g., smart card, or other similar secure storage devices. This provides protection against physical attacks in absence of the token. User Oriented Data Oriented

bzupages.com User Oriented Access Control: User access control in distributed environment can be either centralized or decentralized. 1.In a centralized approach network provides a log on service, determining who is allowed to use the network and to whom the user is allowed to connect. 2.Decentralized user access control treats the network as a transport communication link, and the destination host carries out the usual log on procedure.

bzupages.com User Oriented Access Control: Authenticating users Commonly done using id and password Concern about eavesdropping May be centralized (network logon) or distributed (each host handles logon) May also limit who can access the network as a whole

bzupages.com Data Oriented Access Control: Each user has permitted actions Anyone in administration can see the list of employees, but only personnel staff can change someone’s salary Access matrix (Subjects x Objects) Subject — Entity that can access objects Object — Anything to which access is controlled Access Right — The way the object is accessed by the subject

bzupages.com Data Oriented Access Control: Generally matrix is sparse, so stored in a different fashion: Access Control List Who is allowed to do something with this object Capability List What can this user do?

bzupages.com Javeria Qayyum Topic Access Control

bzupages.com Access Control:

bzupages.com Strategy: Try user info variants Try words from 60,000 entry dictionary Try permutations of above (0-O, 1-L, etc.) Try various capitalization of above

bzupages.com Protecting Password:

bzupages.com Sadia Riaz Topic Auditing

bzupages.com Auditing: Record of ongoing activity Most systems include auditing files Intruder detection system may have additional files Detection-specific audit records Subject — Who is doing the action? Action — What is being done? Object — What is being used? Exception condition — Any problems? Resource usage Timestamp — When did it happen? Each record refers to an elementary action Easier to detect intrusions Simplifies model and implementation

bzupages.com Sana Tareen Topic Fault Tolerance Introduction Requirements

bzupages.com Introduction: What is the System??? 3 Levels of Fault Tolerance 1.H/W fault tolerance 2.S/W fault tolerance 3.System fault tolerance

bzupages.com “A system is the entire set of components, both computer related, and non-computer related, that provides a service to a user.”

bzupages.com Requirements: Dependable System Approaches to achieve dependability 1.Fault avoidance 2.Fault Removal 3.Fault Tolerance Dependability Specification 1.Qualitative 2.Quantitative

bzupages.com Mamoona Sadia Topic Classes of Fault Tolerance Mechanism

bzupages.com Fault Classes: Locality Effects (Timing & Date) Cause (Design, Damage) Duration (Transient, Persistent) Efforts On the System State 1.Crash 2.Amesia

bzupages.com Mechanism: Detection Diagnose Containment

bzupages.com Aliya Zafar Summary of Presentation

bzupages.com Thanks