Network Security Essentials - Notes10. Firewall

Network Security Essentials -- Notes10. Firewall
Firewall's Goals
  1. All traffic must pass through the wall
  2. Only authorized traffic is allowed to pass
  3. Immune to penetration

Techniques
  1.Service Control    -- "This IP is blocked"
  2.Direction Control  -- "Currently we only allow outside traffic"
  3.User Control       -- "You are not allowed to get in"
  4.Behavior Control   -- "You can't send spams to me"


Types of Firewall
   1.Packet-filtering Router -- Filtering based on info in TCP/IP headers, including
      a.Source IP
      b.Destin IP
      c.TCP Port number
      d.IP Protocol Field
      e.Rooter's Interface  (Interface for inside traffic or for outside traffic)

   2.Application-level Gateway = Proxy, inspecting application-level messages
      a.Advantage: More secure than packeting-filter
      b.Disadvantage: Too much additional overhead

   3.Curcuit-level Gateway