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Firewalls

Firewalls. Firewalls. 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 (Only Authorized traffic) The Firewall itself must be immune of attacked.

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Firewalls

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  1. Firewalls

  2. Firewalls • 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 (Only Authorized traffic) • The Firewall itself must be immune of attacked

  3. Firewalls what to configure • 5 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)

  4. Firewalls types • Screening Firewall • The normal built in packet filter firewall in routers • Application Gateway (OR application proxy) • Establish connection to gateway then a new connect out • Have user authentication BUT performance is bad • Circuit level gateway • Like application (two connections + authentication) • Better performance

  5. Firewall – ScreeningPacket-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) • InBound / Outbound on each interface (sometimes also forwarding)

  6. Firewall – ScreeningPacket-filtering • Configurations • Policies: 1:optimistic: default set to allow / forward2:pessimistic: default set to discard / deny • Setting up rules

  7. Example IN OUT IN OUT

  8. Firewall – ScreeningPacket-filtering • Out 10.10.10.1 • In 10.10.10.1

  9. Firewall - Architecture • Best Practice solutionFor small and middle companies: • Screened subnet firewall MOST secure DMZ –demilitarized zone(2 packet-filter + bastion host on the net (DMZ) in between) • Home Firewalllike ZoneAlarm/ windows-firewall

  10. More Literature • SANS (SysAdmin, Audit, Networking, and Security)white paper: • http://www.sans.org/reading-room/whitepapers/firewalls • General information: • http://www.bu.edu/tech/security/firewalls/ • For Unix systems: • https://www.freebsd.org/doc/handbook/firewalls.html • http://www.netfilter.org/ • For Windows: • http://technet.microsoft.com/en-us/library/cc995156.aspx

  11. http://www.kerio.com/download.php?lang=us&product=kwf6-win

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