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Network Security:Pentingnya Keamanan Komputer
Computer Network Research GroupITB
Perspective ...
less then 200 security incident in 1989.
about 400 in 1989.about 1400 in 1993.estimated more than 2241 in 1994.Nobody knows the correct statistics
on how many attacks are actually detected by the sites broken into.
Survey Dan Farmer (Dec96)
1700 web sites:
60% vurnelable.
9-24%terancam jika satu bug dari service daemon (ftpd, httpd / sendmail) ditemukan.
Serangan pada 10-20 % sites di netralisir menggunakan denial-of-service
Statistik Serangan
Jenis Scan Tembus% Kuning% Merah%Banks 660 68.33 32.73 35.61Credit U 274 51.09 30.66 20.44US Fed 47 61.70 23.40 38.30Newspaper 312 69.55 30.77 38.78Sex 451 66.08 40.58 25.50Totals 1734 64.94 33.85 31.08
Resiko Serangan
24
3
0
5
10
15
20
25
W/ Internet W/O Internet
Sumber Serangan
0
20
40
60
80Dari luar
Virus keJ aringan
Virus ke PC
Dari Dalam
Aktifitas Serangan
Manipulasi Data 6.8%Backdoor Software 6.6%Password 5.6%Scanning 14.6%Trojan Horse 5.8%IP Spoofing 4.8%Virus 10.6%
Serangan di Internet
Approx. 19.540.000 hosts are connected to Internet (end1996)
US DoD 250.000 serangan / tahun.Serangan pada Rome Laboratory.
Network Security
usaha untuk mencegah seseorang melakukan tindakan-tindakan yang tidak kita inginkan pada komputer, perangkat lunak, dan piranti yang ada di dalamnya sehingga semuanya tetap dalam keadaan ideal yang kita inginkan’
Layout Firewall
InterNet
InternalNetwork
Firewall
What are you trying to protect?
Your Data.Your Resources.Your Reputation.
What Are You Trying To Protect Against?
Type of attacks
Intrusion.Denial of Service.Information Theft.
Type of Attackers
Joyriders.Vandals.Score Keepers.Spies (Industrial & Otherwise).Stupidity & Accidents.
Security Policy
‘satu keputusan yang menentukan batasan-batasan tindakan-tindakan yang bisa dilakukan dan balasan apabila terjadi pelanggaran batasan-batasan yang ada untuk mencapai satu tujuan tertentu’
Objectives
SecrecyData IntegrityAvailability
Step Security Policy
Apa yang boleh / tidak boleh.Prediksi resiko & biaya (start dengan
bug).Tentukan objek yang di lindungi.Tentukan bentuk ancaman & serangan:
unauthorized access. Disclosure information. Denial of service.
Step ...
Perhatikan kelemahan system: authentication. Password sharing. Penggunaan password yang mudah di
tebak. Software bug.
Optimasi Cost / Performance.
Manusia ...
Tanggung Jawab.Komitmen.
Design Security Policy
Kerahasiaan (Secrecy)Integritas DataAvailabilityKonsistensiKontrol Identifikasi & AuthentikasiMonitoring & Logging
Prinsip ...
Hak minimumKurangi jumlah komponen
How Can You Protect Your Site
No Security.Security Through Obscurity.Host Security.Network Security.No Security Model Can Do It All.
What Can A Firewall Do?
A firewall is a focus for security decisions.
A firewall can enforce security policy.A firewall can log Internet activity
efficiently.A firewall limits your exposure.
What Can’t A Firewall Do?
A firewall can’t protect you against malicious insiders.
A firewall can’t protect you against connections that don’t go through it.
A firewall can’t protect against completely new threats.
A firewall can’t protect against viruses.
List of A Must Secure Internet Services
Electronic mail (SMTP).File Transfer (FTP).Usenet News (NNTP).Remote Terminal Access (Telnet).World Wide Web Access (HTTP).Hostname / Address lookup (DNS).
Security Strategies.Least Privilege.Defense in Depth (multiple security
mechanism).Choke Point forces attackers to use a
narrow channel.Weakest Link.Fail-Safe Stance.Diversity of Defense.Simplicity.
Building Firewalls
Some Firewall Definitions
Firewall A component or set of components that
restricts access between a protected network and the Internet, or between other sets of networks.
Host A computer system attached to a
network.
Firewall Def’s Cont’ ..
Bastion Host A computer system that must be highly
secured because it is vulnerable to attack, usually because it is exposed to the Internet and is a main point of contact for users of internal networks.
Dual-homed host A general-purpose computer system that has
at least two network interfaces (or homes).
Firewall Def’s Cont ...Packet.
The fundamental unit of communication on the Internet.
Packet filtering. The action a device takes to selectively control
the flow of data to and from a network.Perimeter network.
a network added between a protected network and external network, to provide additional layer of security.
Firewall Def’s Cont ...
Proxy Server A program that deals with external
servers on behalf of internal clients. Proxy client talk to proxy servers, which relay approved client requests on to real servers,and relay answer back to clients.
Packet Filtering
InterNet
InternalNetwork
Routes or blocks packets,as determined by site's
security policy.
ScreeningRouter
Proxy Services
InterNet
InternalNetwork
Proxy ServerDual homed HostFirewall
Internal HostProxy Client
External HostReal Server
Screened Host Architecture
InterNet
InternalNetwork
ScreeningRouter
Bastion Host
Firewall
De-Militarized Zone Architecture
InterNet
InternalNetwork
PerimeterNetwork
Interior RouterChoke Router
Exterior Router
Bastion Host
Firewall
DMZ With Two Bastion Hosts
InterNet
InternalNetwork
PerimeterNetwork
Interior RouterChoke Router
Exterior Router
Firewall
SMTP / DNS Host
FTP/WWW Host
It’s OK
Merge Interior & Exterior RouterMerge Bastion Host & Exterior
RouterUse Mutiple Exterior RouterHave Multiple Perimeter NetworkUse Dual -Homed Hosts & Screened
Subnets
It’s Dangerous
Use Multiple Interior RouterMerge Bastion Host and Interior
Router
Private IP Address
Use within Internal NetworkReference RFC 1597IP address alocation:
Class A: 10.x.x.x Class B: 172.16.x.x - 172.31.x.x Class C: 192.168.0.x -
192.168.255.x
Bastion Host
It is our presence in Internet.
Keep it simple.Be prepared for the bastion host to
be compromised.
Special Kinds of Bastion Hosts
Nonrouting Dual-Homed Hosts.Victim Machine.Internal Bastion Hosts.
Choosing A Bastion Host
What Operating System? Unix
How Fast a Machine? 386-based UNIX. MicroVAX II Sun-3
Proxy Systems
Why Proxying? Proxy systems deal with the insecurity
problems by avoiding user logins on the dual-homed host and by forcing connections through controlled software.
It’s also impossible for anybody to install uncontrolled software to reach Internet; the proxy acts as a control point.
Proxy - Reality & Illusion
User's Illusion
Percieved Connection
Actual Connection
Client
ServerProxy Server
Advantages of Proxying
Proxy services allow users to access Internet services “directly”
Proxy services are good at logging.
Disadvantages of ProxyingProxy services lag behind non-proxied
services.Proxy services may require different servers
for each service.Proxy services usually require modifications to
clients, procedures, or both.Proxy services aren’t workable for some
services.Proxy services don’t protect you from all
protocol weaknesses.
Proxying without a Proxy Server
Store-and-Forward services naturally support proxying.
Examples: E-mail (SMTP). News (NNTP). Time (NTP).
Internet Resources on Security Issues
WWW Pages
http://www.telstra.com.au/info/security.html
http://www.cs.purdue.edu/coast/coast.html
Mailing Lists
firewalls@greatcircle.com ftp://ftp.greatcircle.com/pub/firewalls/ http://www.greatcircle.com/firewalls/
fwall-users@tis.comacademic-firewalls@net.tamu.edu
ftp://net.tamu.edu/pub/security/lists/academic-firewalls
bugtraq@fc.net
Newsgroupscomp.security.announce.comp.security.unix.comp.security.misc.comp.security.firewalls.alt.security.comp.admin.policy.comp.protocols.tcp-ip.comp.unix.admin.comp.unix.wizards
Summary
In these dangerous times, firewalls are the best way to keep your site secure.
Although you’ve got to include other tipes of security in the mix, if you’re serious about connecting to the Internet, firewall should be at the very center of your security plans.
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