jan26 - CS 426 class Jan 26, 2012

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CS 426 class Jan 26, 2012 www.cs.purdue.edu/homes/ssw/cs426/{index.html,syll.pdf,outline} (General purpose) Operating System security OS is pgm, so Chapter 3 applies: virus, worm, trapdoor, covert, SE Read Chapter 4 Here we consider security problems specific to OS (no networks yet). History - single user, executive helps; multiuser: monitors What does a (multiuser) OS protect? memory sharable I/O - nonremovable disks serially reusable I/O - printers, tape, removable disks sharable pgms and data OS protects these via kinds of separation: physical (2 printers or cores) temporal (different times) logical (users see no other program) cryptographic (encipher data) Levels of protection (in order easy to hard): none - okay with physical or temporal separation isolation - OS confines each process so that users see no other program share all or share nothing - owner chooses share via access limitation - OS checks each potential access; if <user, object> allowed, okay; OS keeps list share by capabilities - dynamic sharing of rights by owner RWX
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jan26 - CS 426 class Jan 26, 2012

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