Module Three

Screening router n operates at network and transport

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Screening Router n Operates at Network and Transport level n Examines Source and Destination IP Address n Can deny based on ACLs n Can specify Port Application Level Firewall - Second Generation n Proxy Server n Copies each packet from one network to the other n Masks the origin of the data n Operates at layer 7 (Application Layer) n Reduces Network performance since it has do analyze each packet and decide what to do with it. n Also Called Application Layer Gateway Stateful Inspection Firewalls – Third Generation n Packets Analyzed at all OSI layers n Queued at the network level n Faster than Application level Gateway Dynamic Packet Filtering Firewalls – Fourth Generation n Allows modification of security rules n Mostly used for UDP n Remembers all of the UDP packets that have crossed the network’s perimeter, and it decides whether to enable packets to pass through the firewall. Kernel Proxy – Fifth Generation n Runs in NT Kernel n Uses dynamic and custom TCP/IP-based stacks to inspect the network packets and to enforce security policies.
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Firewall Architectures: Packet Filtering Routers: n Sits between trusted and untrusted networks n Uses ACLs n ACLs can be manually intensive to maintain n Lacks strong user authentication n ACLs can degrade performance n Minimal Auditing Screened Host Firewall: n Employs packet filtering and Bastion Host n Provides network layer (packet filtering) and application layer (proxy) services n Penetration requires getting by external router (packet filtering) and Bastion Host (proxy). Dual Homed Host Firewall n Contains two NICs n One connected to the local “trusted” network n One connected to the external “untrusted” network n Blocks or filters traffic between the two. n IP forwarding is disabled
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Screened Subnet Firewall n One of the most secure n Two packet filtering routers and a Bastion Host n Provides network layer (packet filtering) and application layer (proxy) services n Provides DMZ n Complex configuration SOCKS Server n Circuit level proxy server n Requires SOCKS client on all machines n Used to manage outbound Internet access n IT Overhead intensive NAT – Network Address Translation 3 Private IP Address Ranges – Global Nonroutable Addresses 10.0.0.0 to 10.255.255.255 172.16.0.0 to 172.31.255.255 192.168.0.0 to 192.168.255.255 n Class A addresses are for large networks with many devices. 1-127 n Class B addresses are for medium-sized networks. 128-191 n Class C addresses are for small networks (fewer than 256 devices). 192-223 n Class D addresses are multicast addresses . Virtual Private Networks: n Secure connection between two nodes using secret encapsulation method. n Secure Encrypted Tunnel – encapsulated tunnel (encryption may or may not be used) n Tunnel can be created by the following three methods: n Installing software or agents on client or network gateway. n
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Screening Router n Operates at Network and Transport level...

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