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Pertemuan 05Firewall

Matakuliah : H0451/Praktikum Jaringan Komputer

Tahun : 2006

Versi : 1/0

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Learning Outcomes

Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu :

• Menjelaskan mengenai Firewall

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Outline Materi

• Fungsi• Type

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Firewall

• A firewall is hardware or software (or a combination of hardware and software) that monitors the transmission of packets of digital information that attempt to pass through the perimeter or a network.

• A firewall is simply a program or hardware device that filters the information coming through the Internet connection into your private network or Computer system. If an incoming packet of information is flagged by the filters, it is not allowed through.

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• Sole purpose is to filter traffic• Placed at appropriate location in network• Can also be host-based• Performance is important

Firewall

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Perimeter Defense

                                                                                           

                                                        

A firewall is said to provide “perimeter security” because it sits on the outer boundary, or perimeter, or a network. The network boundary is the point at which one network

connects to another.

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Firewall Limitations

• Cannot protect from attacks bypassing it• Cannot protect against internal threats

– e.g. disgruntled employee• Cannot protect against transfer of all virus

infected programs or files– because of huge range of O/S & file types

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• Network firewalls usually run on proprietary or minimized operating systems

• Two approaches to establishing rules– Default permit– Default deny

Characteristic

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• Types– Packet filter– Stateful inspection– Application proxy– Personal

Type Firewall

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Packet Filtering Firewall

• Routers are the most common example– implemented via Access Control Lists

(ACL’s)• Controls access based on src/dest ip

address, port and protocol– does not see the contents of the packet

• Used for egress and ingress filters– ensure outgoing and incoming addresses

are appropriate

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Stateful Inspection Firewall

• Maintains “state” from one packet to another in the network stream

• Tracks the sequence of packets and conditions for packets within a connection– Examine each IP packet in context– Keeps tracks of client-server sessions– Checks each packet validly belongs to one

• Better able to detect bogus packets out of context

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Application Proxy Firewall

• Runs pseudo-applications• Internal clients talk to the proxy and it in

turn talks to the “outside”• More resource intensive on the firewall box

than stateful inspection firewall

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Personal Firewalls

• Application that runs on a workstation (the one being protected) to block unwanted traffic

• Some vended products include host-based intrusion detection features

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Firewall Configurations

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Firewall Configurations

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Firewall Configurations