FIREWALLIDRIS SHAHCIT/20/12
What is a Firewall?• A firewall is simply a program or hardware device that filtersthe information coming through the Inte...
Why firewalls• Protect local systems• Protect network based security threats• Provide secured and controlled access to int...
Types of firewall• Packet filtering firewall applies set of rules to each incoming IP packet and then forwardsor discards...
 Filter packets going in both directions Packet filter set up as list of rules based on matches tofields in TCP or IP he...
advantages• Simplicity• Transparency-need not know about presence offirewall• High speedDisadvantages1.Difficulty of setti...
Application level gateway• Also called proxy server-typically a computer• It is service specific• Acts as a relay of appli...
Advantages• Higher security than packet filters• Only need to scrutinise few allowableapplications• Easy to log and audit ...
Circuit level gateway
• More like tunelling• Standalone system, or specialised functionperformed by application level gateway• Does not permit e...
Bastion Host• It is a system identified by firewalladministrator as critical point in networksecurity• Executes secure ver...
Firewall configurations• In addition to use of simple configuration ofsingle system, more complex configurationsare possib...
Single homed host• Only packets from and to bastion host allowed to passthrough router• Bastion host performs authenticati...
Dual homed host• Packet filtering router not completely compromised• Traffic between internet and hosts on private network...
Screened subnet• Most secure• Two packet filtering routers used• Creation of isolated subnetwork• Inside router accepts pa...
Firewall Limitations• cannot protect from attacks bypassing it• cannot protect against internal threats– e.g. disgruntled ...
Upcoming SlideShare
Loading in...5
×

Firewall

206

Published on

Published in: Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
206
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
14
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Firewall

  1. 1. FIREWALLIDRIS SHAHCIT/20/12
  2. 2. What is a Firewall?• A firewall is simply a program or hardware device that filtersthe information coming through the Internet connection intoyour private network or computer system. If an incomingpacket of information is flagged by the filters, it is not allowedthrough
  3. 3. Why firewalls• Protect local systems• Protect network based security threats• Provide secured and controlled access to internet• Provide restricted and controlled access frominternet to local serversFirewall characteristics• All traffic from outside to inside and vice versamust pass through firewall• Only authorised traffic allowed to pass• Firewall itself immune to penetration
  4. 4. Types of firewall• Packet filtering firewall applies set of rules to each incoming IP packet and then forwardsor discards it. Typically based on ip addresses and port numbers
  5. 5.  Filter packets going in both directions Packet filter set up as list of rules based on matches tofields in TCP or IP header Two default policies( discard or forward).Attacks• IP spoofing• Source routing attack• Tiny fragment attack-first fragment of packet musthave predefined amount of transport header.
  6. 6. advantages• Simplicity• Transparency-need not know about presence offirewall• High speedDisadvantages1.Difficulty of setting up packet filter rules-largerouting tables2. Lack of authentication
  7. 7. Application level gateway• Also called proxy server-typically a computer• It is service specific• Acts as a relay of application level traffic
  8. 8. Advantages• Higher security than packet filters• Only need to scrutinise few allowableapplications• Easy to log and audit all incoming traffic-bactrackingDisadvantagesAdditional processing overhead on eachconnectionSlower as computers not routers
  9. 9. Circuit level gateway
  10. 10. • More like tunelling• Standalone system, or specialised functionperformed by application level gateway• Does not permit end-to-end TCP connection ,rather gateway sets up two TCP connections• Security function consists of determiningwhich connections will be allowed
  11. 11. Bastion Host• It is a system identified by firewalladministrator as critical point in networksecurity• Executes secure version of its OS and istrusted• Consists of services which are essential• Requires additional authentication beforeaccess is allowed
  12. 12. Firewall configurations• In addition to use of simple configuration ofsingle system, more complex configurationsare possible as: Single homed host Dual-homed host Screened subnet
  13. 13. Single homed host• Only packets from and to bastion host allowed to passthrough router• Bastion host performs authentication and proxy functionsGreater security because:• Implements packet and application level filtering• Intruder has to penetrate two seperate systems
  14. 14. Dual homed host• Packet filtering router not completely compromised• Traffic between internet and hosts on private networkhas to flow through bastion host• DMZ-CONTAINS INFO WHICH CAN BE ACCESSED FROMOUTSIDE
  15. 15. Screened subnet• Most secure• Two packet filtering routers used• Creation of isolated subnetwork• Inside router accepts packets only from bastion host
  16. 16. Firewall Limitations• cannot protect from attacks bypassing it• cannot protect against internal threats– e.g. disgruntled employee-intrusion detectionsystems which looks for statistical anamoly.Install personal firewall on desktops• cannot protect against transfer of all virusinfected programs or files– because of huge range of O/S & file types
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×