u9.3 Firewall Types P3. Application Level Proxies

Most complex of the 4 types
1. Does more processing and has more features to support operations on typical networks
  1. provides the most detailed level of control of traffic
    1. checks for correct association of services with port numbers
Do not route packets between source and destination
1. Always repackage the contents of incoming packets into new packets that are generated and sent out from the proxy
The distinction of an application-level proxy firewall is that it actually contains a complete OSI layer 7 client and server implementation for every protocol it can support through the firewall.
1. Normally a machine would be just a client or a server – an application-level proxy firewall has to be both.
  1. This means the security can be very fine grained, more than for any other type of FW
    1. For example a stateful packet might allow HTTP & Block FTP
      1. an ALP can allow GTTP Get but block HTTP Post
        Or allow FTP Get but block exe from being downloaded
    2. Provides a greater level of control at a price
      1. more processing = lowe performance
2. it must contain this functionality for every protocol it may need to send between clients & servers on opposite sides of the FW
  1. the possibilities here mean that ALP end up being extremely complex

Resource summary

	Created by Craig Parker over 10 years ago