53 - Introduction to Operating System Security.md

Importance of OS Security

• Security of computing systems is vital and increasingly important
• OS security is particularly critical because:
  • Everything runs on top of the OS
  • OS has control over all hardware resources
  • OS is large and complex, increasing likelihood of flaws
  • OS must support multiple concurrent processes

What We're Protecting

• Essentially everything the OS controls, including:
  • Process memory
  • Files and storage
  • CPU scheduling
  • Network communication
  • Peripheral devices
  • System calls and OS services

Security Goals and Policies

Key Security Goals

• Confidentiality - Keep sensitive information hidden
• Integrity - Prevent unauthorized changes to data/systems
• Availability - Ensure authorized access to resources

Security Policies

• Specific rules to achieve security goals
• OS provides mechanisms to implement flexible policies
• Policies must be carefully designed and applied

Principles for Designing Secure Systems

• Economy of mechanism - Keep systems simple
• Fail-safe defaults - Default to secure settings
• Complete mediation - Check every access
• Open design - Assume attacker knows system details
• Separation of privilege - Require multiple credentials
• Least privilege - Grant minimal necessary permissions
• Least common mechanism - Separate mechanisms when possible
• Acceptability - Make security usable

Basic OS Security Mechanisms

• Process isolation and virtual memory
• Controlled hardware access
• System call checks
• Access control on OS services

Key Takeaways

• OS security is critical but challenging
• Goals focus on confidentiality, integrity, availability
• Mechanisms enable flexible security policies
• Good design principles help create more secure systems