6.1 Unix Intro

6.1 Unix Intro

1. Originally designed for powerful computing on high end systems

   • Not for PC's

2. Not a single OS but almost a design idea about how to create a system

   • Many different flavors of Unix, HPUX, IBM AIX, Linux

3. Important design features

   • Multi user
     • Multiple users issuing multiple commands at the same time
   • Multi tasking
     • Unix operates multiple commands simultaneously
   • Command line based
     • Mainly a command line based os without a GUI
       • GUI can be added for example Apple's OSX

4. Operates on the onion layer model, with applications at the very outside, kernel, device drivers and hardware at the centre

   • Each layer provides a level of protection from the layer above
     • allows us to identify where where security controls can be applied within the OS
       • A security control in the kernel can restrict what applications can do with the hardware but cant restrict what device drivers might do
   • Users interact with the GUI or CLI, the outside layer.
     • The CLI then interacts with the kernel, protecting the kernel from the user
   • Ultimately the hardware is protected by all the layers
     • The kernel talks to device drivers which then talk to the hardware

5. Not initially designed with security in mind

   • Security features have been added at the command level rather than the kernel
     • Adding security at the command level is less secure, easier to circumvent
     • Security added at the kernel is stronger because the Kernel is closer to the centre of the layered model