FIREWALLS & NETWORK SECURITY with Intrusion Detection and VPNs, 2 nd ed. Chapter 8 Firewall Configuration and Administration

Transcription

1 FIREWALLS & NETWORK SECURITY with Intrusion Detection and VPNs, 2 nd ed. 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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 2

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 3

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 4

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 5

6 Restrictive Firewalls Block all access by default; permit only specific types of traffic to pass through Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 6

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 7

8 Connectivity-Based Firewalls Have fewer rules; primary orientation is to let all traffic pass through and then block specific types of traffic Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 8

9 Firewall Configuration Strategies Criteria Scalable Take communication needs of individual employees into account Deal with IP address needs of the organization Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 9

10 Scalability Provide for the firewall s growth by recommending a periodic review and upgrading software and hardware as needed Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 10

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 11

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) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 12

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) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 13

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 oneto-one association internal to external PAT allows one external address to map to multiple internal addresses Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 14

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 15

16 Encryption (continued) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 16

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 17

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 18

19 Application Proxies on a Dual-Homed Host Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 19

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 20

21 VPN Gateway Bypassing the Firewall Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 21

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 22

23 IDPS Integrated into Perimeter Routers Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 23

24 IDPS Positioned between Firewall and Internet Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 24

25 Enabling a Firewall to Meet New Needs Throughput Scalability Security Recoverability Manageability Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 25

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 26

27 Identifying New Risks Monitor activities and review log files Check Web sites to keep informed of latest dangers; install patches and updates Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 27

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 28

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 29

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) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 30

31 Adhering to Proven Security Principles Generally Accepted System Security Principles (GASSP) apply to ongoing firewall management Secure physical environment where firewallrelated equipment is housed Importance of locking software so that unauthorized users cannot access it Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 31

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 32

33 BIOS, Boot, and Screen Locks BIOS and boot-up passwords Supervisor passwords Screen saver passwords Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 33

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 34

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 35

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 36

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 37

38 Automating Security Checks Outsource firewall management Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 38

39 Configuring Advanced Firewall Functions Ultimate goal High availability Scalability Advanced firewall functions Data caching Redundancy Load balancing Content filtering Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 39

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) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 40

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 41

42 Hot Standby Redundancy (continued) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 42

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 43

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) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 44

45 Load Balancing (continued) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 45

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 46

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) Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 47

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 48

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 49

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 Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 50

51 Chapter Summary (continued) Remote management allows configuration and monitoring of one or more firewalls that are located at different network locations Ultimate goal for many organizations is the development of a high-performance firewall configuration that has high availability and that can be scaled as the organization grows; accomplished by using data caching, redundancy, load balancing, and content filtering Firewalls & Network Security, 2nd ed. - Chapter 8 Slide 51