U2.2 Fundamentals

Annotations:

• 1. Where to FOCUS 2.Where to PLACE 3. Complexity or Assurance 4.Centralise or Decentralise 5. Block access to layer below

1. Dilemma
   1. Security unaware users have specific security requirements but no security expertise
      1. Orange Book
         1. Can predefined evaluation criteria meet specific user requirements
      2. IT SEC
         1. How can a security unaware user assess a specific target of valuation
2. 1st Design Decision
   1. Where to focus Sec Ctrls
      1. Can be placed almost anywhere
         1. Tends to be on Data and Users, sometimes Operations
         2. Controls can be enforcd by the operating system
         3. Controls can be procedural
3. 2nd Design Descision
   1. Where to place Sec Ctrls
      1. Can be placed at any layer from App to Physical
         1. As you move down the layers you apply a more universal control
            1. The lower you go the more flexibility is compromised
               1. Application Sec provides greater flexibility
         2. Higher layers are more complex to secure, most expensive and more dev time required
      2. Man - Machine Scale
4. 3rd Decision
   1. Complexity or Assurance
      1. Hardware based = Simple controls
      2. Application Based = feature rich & complex
      3. Problem is, simplicity gives higher assurance levels of secuirity
      4. To achieve high assurance products must be examined in great detail
         1. Complex controls are harder to analyse and therefore harder to provide great arrurances
         2. Obvious tradeoff between complexity and assurance
5. 4th Descision
   1. Centralise or decentralise control
      1. Single entity
         1. Consistent, Uniform, may become less efficient
      2. Distributed Control
         1. More efficient but more management and concerns about consistency
6. 5th Descision
   1. Blocking access to the layer below
      1. Protection mechanisims define a security perimiter
         1. Once an attacker is inside, defence it breached
      2. If a particular Sec mech is placed at the services layer, how do you stop an attacker from defeating that mechanisim by breaking the OS at the layer below
         1. A total solution is required