QMCS 490 - Class Today

1
QMCS 490 - Class Today

• Homework collect/return
• OS Security/Policy
• OS Security/Techniques
• Trojan Horse
• Encrypting a File/PGP

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Security Perimeters/Sharing/Policy

• Pretty good, overall
• Important points
• Distinguish between known agreements and
  behaviors, and the rationale behind them
• They have their own computers, so wasnt asked
• Its understood (or not) about sharing - WAS
  asked
• Note the features that make protection stronger,
  like locks and barriers (doors, walls)
• Being in a room with the door closed is better
  than being left on a bench in a public park -
  GIVEN THE THREATS
• What if threats know your machine has valuable
  stuff?
• The Antiques Roadshow dilemma - nobody wants to
  steal it if its priceless but nobody knows
• If theres no reason to seek it out, its safer
• Tragedy of the Commons

3
What IS an operating system?

• Could someone point it out to me, please?

4
Operating Systems Policy

• What are we trying to protect?
• What are the operating goals?

5
Pieces of an OS

• Bootup software - gets things started
• I/O management - controls the hard drives, kb,
  mouse, monitor, etc.
• Process management - starts up programs for
  users, and for the OS itself
• Memory management - arranges RAM for user
  programs and for OS activities
• File management - handles storage on the hard
  drive so you can find and store things there
• Operator interface - control the OS and start up
  programs

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How can an OS protect itself?

• What are the risks?
• User A damaging User Bs files
• Program X crashing Program Y
• Program X damaging OS data
• Program X damaging OS programs on disk
• File permissions - the tip of the iceberg
• Restrictions on processes
• Restrictions on RAM
• Protection is layered up through file system
• Privileged programs
• Device drivers and kernel mode
• Kernel loadable modules

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Windows and Privileged Software

• Privileges tied to accounts
• Programs/objects inherit them from users process
• Can be granted to a user ID or a group
• Example privileges
• login interactively or over network or as service
• Setting the clock or time zone
• Shutdown, undock machine
• Load device driver
• Create special system files, like page file

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The Trojan Horse and file hacking

• Transitive trust
• Data leakage and the shared file system
• Diagram!

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