Security Issues

Security Issues

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. ●

Layout Firewall In te r N e t

F ir e w a ll

In te r n a l N e tw o rk

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. ●

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.

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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.

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Packet filtering. – The action a device takes to selectively control the flow of data to and from a network.

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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 In te r N e t

R o u te s o r b lo c k s p a c k e ts , a s d e t e r m i n e d b y s i t e 's s e c u r ity p o lic y .

S c r e e n in g R o u te r

In te r n a l N e tw o rk

Proxy Services In te r N e t E x te rn a l H o s t R ea l S erve r

P ro xy S erve r D ual hom ed H ost

F ir e w a ll

In te r n a l N e tw o rk In te r n a l H o s t P r o x y C lie n t

Screened Host Architecture In te r N e t F ir e w a ll S c r e e n in g R o u te r

B a s tio n H o s t

In te r n a l N e tw o rk

De-Militarized Zone Architecture

F ir e w a ll

In te r N e t

E x te r io r R o u te r

B a s tio n H o s t

In te r n a l N e tw o rk

P e r im e t e r N e tw o rk In te r io r R o u te r C h o k e R o u te r

DMZ With Two Bastion Hosts F ir e w a ll In t e r N e t

E x te rio r R o u te r

F T P /W W W H o s t

In te r n a l N e tw o rk

P e r im e t e r N e tw o rk In te r io r R o u te r C h o k e R o u te r

SM TP / DNS Host

It’s OK Merge Interior & Exterior Router ● Merge Bastion Host & Exterior Router ● Use Mutiple Exterior Router ● Have Multiple Perimeter Network ● Use Dual -Homed Hosts & Screened Subnets ●

It’s Dangerous Use Multiple Interior Router ● Merge Bastion Host and Interior Router ●

Private IP Address Use within Internal Network ● Reference RFC 1597 ● IP address alocation: ●

– Class A: – Class B: – Class C:

10.x.x.x 172.16.x.x - 172.31.x.x 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 dualhomed 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 P e r c ie v e d C o n n e c tio n A c tu a l C o n n e c tio n

Real Ser

P ro x y S e rv e r C lie n t U s e r 's I l l u s i o n

ver's Il

lusio n

S e rv e r

Advantages of Proxying Proxy services allow users to access Internet services “directly” ● Proxy services are good at logging. ●

Disadvantages of Proxying Proxy 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 ●

[email protected] – ftp://ftp.greatcircle.com/pub/firewalls/ – http://www.greatcircle.com/firewalls/

[email protected] ● [email protected] ●

– ftp://net.tamu.edu/pub/security/lists/academicfirewalls ●

[email protected]

Newsgroups comp.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 types 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. ●