Matakuliah
Tahun
Versi
: H0451/Praktikum Jaringan Komputer
: 2006
: 1/0
Pertemuan 05
Firewall
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Menjelaskan mengenai Firewall
2
Outline Materi
• Fungsi
• Type
3
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.
4
Firewall
•
•
•
•
Sole purpose is to filter traffic
Placed at appropriate location in network
Can also be host-based
Performance is important
5
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.
6
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
7
Characteristic
• Network firewalls usually run on
proprietary or minimized operating
systems
• Two approaches to establishing rules
– Default permit
– Default deny
8
Type Firewall
• Types
– Packet filter
– Stateful inspection
– Application proxy
– Personal
9
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
10
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
11
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
12
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
13
Firewall Configurations
14
Firewall Configurations
15
Firewall Configurations
16