Download Firewalls - Eastern Michigan University

Firewalls
 Screen packets coming into the Privet
Networks from external, Untrusted Networks
(Internet)
 Ingress Packet Filtering
Firewall examine incoming packet and either pass or
drop (deny) the packet
 Egress Packet Filtering
Firewall examine the packet when the packet is leaving
the internal network
Border Firewall
Internal
Corporate
Network
(Trusted)
PC
Switch
Egress
Passed
Packet
Ingress
Passed
Packet
Attacker
Border Firewall
Dropped
Packet
Logs
Server
Internal
Corporate
Network
(Trusted)
Internet
(Not Trusted)
Firewalls – Type of Protection
Packet Inspection
IP, TCP, UDP, ICMP
Static packet filtering (Stateless filtering)
Stateful filtering
Application Inspection
Application Layer messages
Stop malicious executable attachment
Network Address Translation (NAT)
Spoofs the IP addresses of outgoing packets
Firewalls – Type of Protection
Denial-of-Services Inspection
SYN Flood
Cisco PIX – TCP intercept
Authentication
Only allow the packets from authenticated user
Not common
Virtual Private Networking
Usually work with authentication
Provide confidentiality
Firewall Hardware and Software
Screening Router Firewall
High Cost
Good place for Egress Filtering
Computer-based Firewalls
Lower Cost
Ease of use
Higher risk on Operating System part
Firewall Hardware and Software
Firewall Appliances
Like your toaster
Provide rules update
Host Firewalls
Individual client or server host
Defense in depth
Hard to manage
Static Packet Filter Firewalls
The Internet
Corporate Network
Arriving Packets
| IP-H | TCP-H | Application Message |
| IP-H | UDP-H | Application Message |
| IP-H | ICMP Message
|
| All Permitted Packets |
Denied Packets
Static Packet Filter
Log File
Access Control Lists (ACLs)
The way to organize the filtering rules
Use If-then Format
Sequential Rule Evaluation
Deny All
Access Control Lists (ACLs)
The way to organize the filtering rules
Use If-then Format
Sequential Rule Evaluation
Deny All
Sensitivity to Misordering
GUI Firewall Rule Maker