Skip to main content

Foundations

Defining Security​

Security = Protection of assets Security Policy = Concise document explaining the needs

Computer security is usually defined as three key areas (CIA)

  • Confidentiality - Prevention of unauthorised disclosure of information
    • Privacy - medical records etc
  • Integrity - Prevention of unauthorised modification of information
    • Changing database records
  • Availability - Prevention of unauthorised withholding of information or resource
    • Prevent DoS attacks

Accountability - Users should be held responsible for their actions, audit trails must be kept Non-repudiation - Provides an un-forgeable evidence that someone did something, mostly a legal concept. Applies to physical security (key cards)

Security-unaware users have specific security requirements but no security expertise

Trade-offs of computer security come down to the threats and specific situation

Security Design​

  • Approach should be systematic, disciplined and well planned
  • From the inception/design of a system
  • If added afterwards, could lead to disaster

Good design focuses on 4 principles:

Focus of Control​

  • Data - Permitted manipulation of data e.g consistency check
  • Operations - Permitted invocations e.g. transfermoney()
  • Users - Permissions for specific users

Complexity vs. Assurance​

Would we prefer a simple approach with high assurance? Or a feature-rich environment?

Feature-rich security systems and high assurance do not match easily e.g Linux vs Windows permissions

Centralised or Decentralised Controls​

Should defining and enforcing security be performed by a central entity, or be left to individual components in a system

Central Entity - A possible bottleneck Distributed So9lution - More efficient, but harder to manage

Layered Security​

We can visualise our security model in layers Each layer protects a boundary, and relies on the security of the layers below

Applications > Services > OS > Kernel > Hardware

Attack the layer below:​