ISA 3200 Network Security

1. ISA 3200Network Security Chapter 8: Firewall Configuration and Administration

2. Learning Objectives • Set up firewall rules that reflect an organization’s overall security approach • Identify and implement different firewall configuration strategies • Update a firewall to meet new needs and threats • Adhere to proven security principles to help the firewall protect network resources IS 3200, Summer 2010

3. Learning Objectives (continued) • Use a remote management interface • Track firewall log files and follow the basic initial steps in responding to security incidents • Understand the nature of advanced firewall functions IS 3200, Summer 2010

4. Establishing Firewall Rules and Restrictions • Rules give firewalls specific criteria for making decisions about whether to allow packets through or drop them • All firewalls have a rules file—the most important configuration file on the firewall IS 3200, Summer 2010

5. The Role of the Rules File • Establishes the order the firewall should follow • Tells the firewall which packets should be blocked and which should be allowed • Requirements • Need for scalability • Importance of enabling productivity of end users while maintaining adequate security IS 3200, Summer 2010

6. Restrictive Firewalls • Block all access by default; permit only specific types of traffic to pass through IS 3200, Summer 2010

7. Restrictive Firewalls (continued) • Follow the concept of least privilege • Spell out services that employees cannot use • Use and maintain passwords • Choose an approach • Open • Optimistic • Cautious • Strict • Paranoid IS 3200, Summer 2010

8. Connectivity-Based Firewalls • Have fewer rules; primary orientation is to let all traffic pass through and then block specific types of traffic IS 3200, Summer 2010

9. Firewall Configuration Strategies • Criteria • Scalable • Take communication needs of individual employees into account • Deal with IP address needs of the organization IS 3200, Summer 2010

10. Scalability • Provide for the firewall’s growth by recommending a periodic review and upgrading software and hardware as needed IS 3200, Summer 2010

11. Productivity • The stronger and more elaborate the firewall, the slower the data transmissions • Important features of firewall: processing and memory resources available to the bastion host IS 3200, Summer 2010

12. Dealing with IP Address Issues • If service network needs to be privately rather than publicly accessible, which DNS will its component systems use? • If you mix public and private addresses, how will Web server and DNS servers communicate? • Let the proxy server do the IP forwarding (it’s the security device) IS 3200, Summer 2010

13. Approaches That Add Functionality to Your Firewall • Network Address Translation (NAT) • Port Address Translation (PAT) • Encryption • Application proxies • VPNs • Intrusion Detection and Prevention Systems (IDPSs) IS 3200, Summer 2010

14. NAT/PAT • NAT and PAT convert publicly accessible IP addresses to private ones and vice versa; shields IP addresses of computers on the protected network from those on the outside • Where NAT converts these addresses on a one-to-one association—internal to external—PAT allows one external address to map to multiple internal addresses IS 3200, Summer 2010

15. Encryption • Takes a request and turns it into gibberish using a private key; exchanges the public key with the recipient firewall or router • Recipient decrypts the message and presents it to the end user in understandable form IS 3200, Summer 2010

16. Encryption (continued) IS 3200, Summer 2010

17. Application Proxies • Act on behalf of a host; receive requests, rebuild them from scratch, and forward them to the intended location as though the request originated with it (the proxy) • Can be set up with either a dual-homed host or a screened host system IS 3200, Summer 2010

18. Application Proxies (continued) • Dual-homed setup • Host that contains the firewall or proxy server software has two interfaces, one to the Internet and one to the internal network being protected • Screened subnet system • Host that holds proxy server software has a single network interface • Packet filters on either side of the host filter out all traffic except that destined for proxy server software IS 3200, Summer 2010

19. Application Proxies on aDual-Homed Host IS 3200, Summer 2010

20. VPNs • Connect internal hosts with specific clients in other organizations • Connections are encrypted and limited only to machines with specific IP addresses • VPN gateway can: • Go on a DMZ • Bypass the firewall and connect directly to the internal LAN IS 3200, Summer 2010

21. VPN Gateway Bypassing the Firewall IS 3200, Summer 2010

22. Intrusion Detection and Prevention Systems • Can be installed in external and/or internal routers at the perimeter of the network • Built into many popular firewall packages IS 3200, Summer 2010

23. IDPS Integrated into Perimeter Routers IS 3200, Summer 2010

24. IDPS Positioned between Firewall and Internet IS 3200, Summer 2010

25. Enabling a Firewall to Meet New Needs • Throughput • Scalability • Security • Recoverability • Manageability IS 3200, Summer 2010

26. Verifying Resources Needed by the Firewall • Ways to track memory and system resources • Use the formula:MemoryUsage = ((ConcurrentConnections)/ (AverageLifetime))*(AverageLifetime + 50 seconds)*120 • Use software’s own monitoring feature IS 3200, Summer 2010

27. Identifying New Risks • Monitor activities and review log files • Check Web sites to keep informed of latest dangers; install patches and updates IS 3200, Summer 2010

28. Adding Software Updates and Patches • Test updates and patches as soon as you install them • Ask vendors (of firewall, VPN appliance, routers, etc.) for notification when security patches are available • Check manufacturer’s Web site for security patches and software updates IS 3200, Summer 2010

29. Adding Hardware • Identify network hardware so firewall can include it in routing and protection services • Different ways for different firewalls • List workstations, routers, VPN appliances, and other gateways you add as the network grows • Choose good passwords that you guard closely IS 3200, Summer 2010

30. Dealing with Complexity on the Network • Distributed firewalls • Installed at endpoints of the network, including remote computers that connect to network through VPNs • Add complexity • Require that you install and/or maintain a variety of firewalls located on your network and in remote locations • Add security • Protect network from viruses or other attacks that can originate from machines that use VPNs to connect (e.g., remote laptops) IS 3200, Summer 2010

31. Adhering to Proven Security Principles • Generally Accepted System Security Principles (GASSP) apply to ongoing firewall management • Secure physical environment where firewall-related equipment is housed • Importance of locking software so that unauthorized users cannot access it IS 3200, Summer 2010

32. Environmental Management • Measures taken to reduce risks to physical environment where resources are stored • Back-up power systems overcome power outages • Back-up hardware and software help recover network data and services in case of equipment failure • Sprinkler/alarm systems reduce damage from fire • Locks guard against theft IS 3200, Summer 2010

33. BIOS, Boot, and Screen Locks • BIOS and boot-up passwords • Supervisor passwords • Screen saver passwords IS 3200, Summer 2010

34. Remote Management Interface • Software that enables you to configure and monitor firewall(s) that are located at different network locations • Used to start/stop the firewall or change rule base from locations other than the primary computer IS 3200, Summer 2010

35. Why Remote Management Tools Are Important • Reduce time and make the job easier for the security administrator • Reduce chance of configuration errors that might result if the same changes were made manually for each firewall on the network IS 3200, Summer 2010

36. Security Concerns • Can use a Security Information Management (SIM) device to prevent unauthorized users from circumventing security systems • Offers strong security controls (e.g., multi-factor authentication and encryption) • Should have an auditing feature • Should use tunneling to connect to the firewall or use certificates for authentication • Evaluate SIM software to ensure it does not introduce new vulnerabilities IS 3200, Summer 2010

37. Basic Features of Remote Management Tools • Ability to monitor and configure firewalls from a single centralized location • View and change firewall status • View firewall’s current activity • View any firewall event or alert messages • Ability to start and stop firewalls as needed IS 3200, Summer 2010

38. Automating Security Checks • Outsource firewall management IS 3200, Summer 2010

39. Configuring Advanced Firewall Functions • Ultimate goal • High availability • Scalability • Advanced firewall functions • Data caching • Redundancy • Load balancing • Content filtering IS 3200, Summer 2010

40. Data Caching • Set up a server that will: • Receive requests for URLs • Filter those requests against different criteria • Options • No caching • URI Filtering Protocol (UFP) server • VPN & Firewall (one request) • VPN & Firewall (two requests) IS 3200, Summer 2010

41. Hot Standby Redundancy • Secondary or failover firewall is configured to take over traffic duties in case primary firewall fails • Usually involves two firewalls; only one operates at any given time • The two firewalls are connected in a heartbeat network IS 3200, Summer 2010

42. Hot Standby Redundancy (continued) IS 3200, Summer 2010

43. Hot Standby Redundancy (continued) • Advantages • Ease and economy of setup and quick backup system it provides for the network • One firewall can be stopped for maintenance without stopping network traffic • Disadvantages • Does not improve network performance • VPN connections may or may not be included in the failover system IS 3200, Summer 2010

44. Load Balancing • Practice of balancing the load placed on the firewall so that it is handled by two or more firewall systems • Load sharing • Practice of configuring two or more firewalls to share the total traffic load • Traffic between firewalls is distributed by routers using special routing protocols • Open Shortest Path First (OSPF) • Border Gateway Protocol (BGP) IS 3200, Summer 2010

45. Load Balancing (continued) IS 3200, Summer 2010

46. Load Sharing • Advantages • Improves total network performance • Maintenance can be performed on one firewall without disrupting total network traffic • Disadvantages • Load usually distributed unevenly (can be remedied by using layer four switches) • Configuration can be complex to administer IS 3200, Summer 2010

47. Filtering Content • Firewalls don’t scan for viruses but can work with third-party applications to scan for viruses or other functions • Open Platform for Security (OPSEC) model • Content Vectoring Protocol (CVP) IS 3200, Summer 2010

48. Filtering Content (continued) • Install anti-virus software on SMTP gateway in addition to providing desktop anti-virus protection for each computer • Choose an anti-virus gateway product that: • Provides for content filtering • Can be updated regularly to account for recent viruses • Can scan the system in real time • Has detailed logging capabilities IS 3200, Summer 2010

49. Chapter Summary • After establishing a security policy, implement the strategies that policy specifies • If primary goal of planned firewall is to block unauthorized access, you must emphasize restricting rather than enabling connectivity • A firewall must be scalable so it can grow with the network it protects • The stronger and more elaborate your firewall, the slower data transmissions are likely to be • The more complex a network becomes, the more IP-addressing complications arise IS 3200, Summer 2010

50. Chapter Summary (continued) • Network security setups can become more complex when specific functions are added • Firewalls must be maintained regularly to assure critical measures of success are kept within acceptable levels of performance • Successful firewall management requires adherence to principles that have been put forth by reputable organizations to ensure that firewalls and network security configurations are maintained correctly IS 3200, Summer 2010