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Firewall – Survey

Firewall – Survey. Purpose of a Firewall To allow ‘proper’ traffic and discard all other traffic Characteristic of a firewall All traffic must go through the firewall Allow and blocking traffic The Firewall itself should be immune of attacked. Firewall – possibilities.

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Firewall – Survey

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  1. Firewall – Survey • Purpose of a Firewall • To allow ‘proper’ traffic and discard all other traffic • Characteristic of a firewall • All traffic must go through the firewall • Allow and blocking traffic • The Firewall itself should be immune of attacked

  2. Firewall – possibilities • 5(6) areas to control: • Services (web, ftp, mail …) i.e. Port# • Network (hosts) i.e. IP addresses • Direction i.e. control inside-out or reverse • User i.e. only authorized users allow • Behaviour (e.g. attachment to mail) • (Denial of Service Inspection)

  3. Firewall – solutions • Solutions: • HW – screening router • SW – Computer Based (build in the OS) • SW – dedicated Host Firewall

  4. Firewall – limitations • 3 limitations of Firewalls • Cannot protect against traffic not running trough the firewall (obvious!!) • Cannot protect against threats from inside(e.g. as the school network) • Cannot protect against viruses (i.e. they come in by legal traffic)

  5. Firewall – Types • 3 types of Firewalls • Packet-filtering • Packet-filtering – with state-full inspection • Application- gateways

  6. Firewall – Packet-filtering • Level 3 – network (IP-packets) • Filtering on (the access control list): • Source/Destination IP-addresses • Source/Destination Port-numbers • IP-protocol field (e.g. icmp, tcp, egp) • TCP-direction (SYN-bit) • IN / OUT on each interface • ICMP message type

  7. Firewall – Packet-filtering • Configurations • Policies: 1:optimistic: default set to allow2:pessimistic: default set to discard (normal) • Setting up rules

  8. Firewall – Packet-filtering • Weakness • Cannot ‘look’ into appl. Level information • Limited logging information • Do normally not support authentication • Can be attack by weakness in IP (e.g. IP-spoofing)

  9. Firewall – Packet-filtering • Stateful - inspection • Normal packet-filtering only look at one packet at a time. • Stateful packet-filtering can remember a sequence of packets.(can be used to detect spoofing)

  10. Firewall – Application-level • Level 5 Application gateway • Using Proxy Servers(e.g. a mail-client and a mail-server) • Spilt connections into 2 (one for inbound and one for outbound)

  11. Firewall – Application-level • More secure • Stateful inspection even more developed • User authentication are used • Weakness • slow-down performance • need to have proxies for all services

  12. Intrusion System • Deep packet inspection • Read and remember history of packets • Two types • Intrusion Detection System (IDS) • Send alert if behaviour is odd • One implementation snort (open source / Linux) • Intrusion Prevention System (IPS) • Filter out suspicious packets

  13. Firewall – Architecture • One recommended solution: • Screened subnet firewall MOST secure DMZ –demilitarized zone(2 packet-filter + bastion host on the net (DMZ) in between) • Home Firewalllike ZoneAlarm/Windows-firewall

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