Firewall and its purpose


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An insight into the mechanism of firewall of windows and other operating systems


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Firewall and its purpose

  1. 1. FIRE
  2. 2. WALL
  3. 3. + =But does fire + wall =firewall ??? Is this definitioncorrect??Well not exactly 
  4. 4. Finally, welcome to last presentation of the 8th SEM CSE
  5. 5. FIREWALLSPresented by-1) Rohit Phulsunge2) Satyendra Singh Naruka3) Saurabh Maheswari4) Sameer Pathak5) Sandeep Suryawanshi
  6. 6. So what exaclty is a firewall?? A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass.
  7. 7. A diagram showing where afirewall can be placed.
  8. 8. History The term firewall originally referred to a wall intended to confine a fire or potential fire within a building Later uses refer to similar structures, such as the metal sheet separating the engine compartment of a vehicle or aircraft from the passenger compartment.
  9. 9. What does firewall do? a choke point of control and monitoring interconnects networks with differing trust imposes restrictions on network services ◦ only authorized traffic is allowed auditing and controlling access ◦ can implement alarms for abnormal behavior provide NAT & usage monitoring
  10. 10. Firewall Limitations cannot protect from attacks bypassing it ◦ E.g., sneaker net, utility modems, trusted organisations, trusted services (eg SSL/SSH) cannot protect against internal threats ◦ eg disgruntled or colluding employees cannot protect against transfer of all virus infected programs or files ◦ because of huge range of O/S & file types
  11. 11. Firewalls – Packet Filters simplest, fastest firewall component foundation of any firewall system examine each IP packet (no context) and permit or deny according to rules hence restrict access to services (ports) possible default policies ◦ that not expressly permitted is prohibited ◦ that not expressly prohibited is permitted 12
  12. 12. Firewalls – Packet Filters 13
  13. 13. Firewalls – Packet Filters 14
  14. 14. Attacks on Packet Filters IP address spoofing ◦ fake source address ◦ authenticate source routing attacks ◦ attacker sets a route other than default ◦ block source routed packets tiny fragment attacks ◦ split header info over several tiny packets ◦ either discard or reassemble before check 15
  15. 15. Firewalls – Stateful PacketFilters traditional packet filters do not examine higher layer context ◦ i.e., matching return packets with outgoing flow stateful packet filters address this need they examine each IP packet in context ◦ keep track of client-server sessions ◦ check each packet validly belongs to one they are better able to detect bogus packets out of context 16
  16. 16. TYPES OF FIREWALLS Packet filtering Router Application level gateway Circuit level gateway 17
  17. 17. Packet filtering RouterApply set of rules to IP packet*Rules for network packet Source IP Address Destination IP Address Source & Destination transport level address IP protocol field Interface 18
  18. 18. Application Level Gateway have application specific gateway / proxy has full access to protocol ◦ user requests service from proxy ◦ proxy validates request as legal ◦ then actions request and returns result to user ◦ can log / audit traffic at application level 19
  19. 19. Application Level Gateway 20
  20. 20. Firewalls - Circuit LevelGateway relays two TCP connections imposes security by limiting what such connections are allowed once created usually relays traffic without examining contents typically used when trust internal users by allowing general outbound connections 21
  21. 21. Firewalls - Circuit LevelGateway 22
  22. 22. Bastion Host highly secure host system runs circuit / application level gateways or provides externally accessible services potentially exposed to "hostile" elements hence is secured to withstand this ◦ hardened O/S, essential services, extra auth 23
  23. 23. Firewall Configurations 24
  24. 24. Firewall Configurations 25
  25. 25. Firewall Configurations 26
  26. 26. Access Control determines what resources users can access general model is that of access matrix with ◦ subject - active entity (user, process) ◦ object - passive entity (file or resource) ◦ access right – way object can be accessed can decompose by ◦ columns as access control lists ◦ rows as capability tickets 27
  27. 27. Access Control Matrix 28
  28. 28. Trusted Computer Systems information security is increasingly important have varying degrees of sensitivity of information ◦ military info classifications: confidential, secret, etc subjects (people or programs) have varying rights of access to objects (information) known as multilevel security ◦ subjects have maximum & current security level ◦ objects have a fixed security level classification want to consider ways of increasing confidence in systems to enforce these 29
  29. 29. Bell LaPadula (BLP) Model has two key policies: no read up (simple security property) ◦ a subject can only read an object if the current security level of the subject dominates (>=) the classification of the object no write down (*-property) ◦ a subject can only append/write to an object if the current security level of the subject is dominated by (<=) the classification of the object 30
  30. 30. Reference Monitor 31
  31. 31. Summary have considered: ◦ firewalls ◦ types of firewalls ◦ configurations ◦ access control ◦ trusted systems 32