Security+ Guide to Network Security Fundamentals, Fourth Edition. Chapter 6 Network Security

Transcription

1 Security+ Guide to Network Security Fundamentals, Fourth Edition Chapter 6 Network Security

2 Objectives List the different types of network security devices and explain how they can be used Define network address translation and network access control Explain how to enhance security through network design Security+ Guide to Network Security Fundamentals, Fourth Edition 2

3 Security Through Network Devices Not all applications designed, written with security in mind Network must provide protection Networks with weak security invite attackers Aspects of building a secure network Network devices Network technologies Design of the network itself Security+ Guide to Network Security Fundamentals, Fourth Edition 3

4 Standard Network Devices Security features found in network hardware Provide basic level of security Open systems interconnection (OSI) model Network devices classified based on function Standards released in 1978, revised in 1983, still used today Illustrates: How network device prepares data for delivery How data is handled once received Security+ Guide to Network Security Fundamentals, Fourth Edition 4

5 Standard Network Devices (cont d.) OSI model breaks networking steps into seven layers Each layer has different networking tasks Each layer cooperates with adjacent layers Security+ Guide to Network Security Fundamentals, Fourth Edition 5

6 Table 6-1 OSI reference model Security+ Guide to Network Security Fundamentals, Fourth Edition 6

7 Standard Network Devices (cont d.) Hubs Connect multiple Ethernet devices together: To function as a single network segment Use twisted-pair copper or fiber-optic cables Work at Layer 1 of the OSI model Do not read data passing through them Ignorant of data source and destination Rarely used today because of inherent security vulnerability Security+ Guide to Network Security Fundamentals, Fourth Edition 7

8 Standard Network Devices (cont d.) Switches Network switch connects network segments Operate at Data Link Layer (Layer 2) Determine which device is connected to each port Can forward frames sent to that specific device Or broadcast to all devices Use MAC address to identify devices Provide better security than hubs Security+ Guide to Network Security Fundamentals, Fourth Edition 8

9 Standard Network Devices (cont d.) Network administrator should be able to monitor network traffic Helps identify and troubleshoot network problems Traffic monitoring methods Port mirroring Network tap (test access point) Separate device installed between two network devices Security+ Guide to Network Security Fundamentals, Fourth Edition 9

10 Figure 6-1 Port mirroring Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 10

11 Figure 6-2 Network tap Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 11

12 Table 6-2 Protecting the switch Security+ Guide to Network Security Fundamentals, Fourth Edition 12

13 Standard Network Devices (cont d.) Routers Forward packets across computer networks Operate at Network Layer (Layer 3) Can be set to filter out specific types of network traffic Load balancers Help evenly distribute work across a network Allocate requests among multiple devices Security+ Guide to Network Security Fundamentals, Fourth Edition 13

14 Standard Network Devices (cont d.) Advantages of load-balancing technology Reduces probability of overloading a single server Optimizes bandwidth of network computers Reduces network downtime Load balancing is achieved through software or hardware device (load balancer) Security+ Guide to Network Security Fundamentals, Fourth Edition 14

15 Standard Network Devices (cont d.) Security advantages of load balancing Can stop attacks directed at a server or application Can detect and prevent denial-of-service attacks Some can deny attackers information about the network Hide HTTP error pages Remove server identification headers from HTTP responses Security+ Guide to Network Security Fundamentals, Fourth Edition 15

16 Network Security Hardware Specifically designed security hardware devices Greater protection than standard networking devices Firewalls Hardware-based network firewall inspects packets Can either accept or deny packet entry Usually located outside network security perimeter Security+ Guide to Network Security Fundamentals, Fourth Edition 16

17 Figure 6-3 Firewall location Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 17

18 Network Security Hardware (cont d.) Firewall actions on a packet Allow (let packet pass through) Block (drop packet) Prompt (ask what action to take) Rule-based firewall settings Set of individual instructions to control actions Settings-based firewall Allows administrator to create parameters Security+ Guide to Network Security Fundamentals, Fourth Edition 18

19 Table 6-3 Rule for Web page transmission Security+ Guide to Network Security Fundamentals, Fourth Edition 19

20 Network Security Hardware (cont d.) Methods of firewall packet filtering Stateless packet filtering Inspects incoming packet and permits or denies based on conditions set by administrator Stateful packet filtering Keeps record of state of connection Makes decisions based on connection and conditions Security+ Guide to Network Security Fundamentals, Fourth Edition 20

21 Network Security Hardware (cont d.) Web application firewall Looks deeply into packets that carry HTTP traffic Web browsers FTP Telnet Can block specific sites or specific known attacks Can block XSS and SQL injection attacks Security+ Guide to Network Security Fundamentals, Fourth Edition 21

22 Network Security Hardware (cont d.) Proxies Devices that substitute for primary devices Proxy server Computer or application that intercepts and processes user requests If a previous request has been fulfilled: Copy of the Web page may reside in proxy server s cache If not, proxy server requests item from external Web server using its own IP address Security+ Guide to Network Security Fundamentals, Fourth Edition 22

23 Figure 6-4 Proxy server Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 23

24 Figure 6-5 Configuring access to proxy servers Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 24

25 Network Security Hardware (cont d.) Proxy server advantages Increased speed (requests served from the cache) Reduced costs (cache reduces bandwidth required) Improved management Block specific Web pages or sites Stronger security Intercept malware Hide client system s IP address from the open Internet Security+ Guide to Network Security Fundamentals, Fourth Edition 25

26 Network Security Hardware (cont d.) Reverse proxy Does not serve clients Routes incoming requests to correct server Reverse proxy s IP address is visible to outside users Internal server s IP address hidden Security+ Guide to Network Security Fundamentals, Fourth Edition 26

27 Figure 6-6 Reverse proxy Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 27

28 Network Security Hardware (cont d.) Spam filters Enterprise-wide spam filters block spam before it reaches the host systems use two protocols Simple Mail Transfer Protocol (SMTP) Handles outgoing mail Post Office Protocol (POP) Handles incoming mail Security+ Guide to Network Security Fundamentals, Fourth Edition 28

29 Network Security Hardware (cont d.) Spam filters installed with the SMTP server Filter configured to listen on port 25 Pass non-spam to SMTP server listening on another port Method prevents SMTP server from notifying spammer of failed message delivery Security+ Guide to Network Security Fundamentals, Fourth Edition 29

30 Figure 6-7 Spam filter with SMTP server Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 30

31 Network Security Hardware (cont d.) Spam filters installed on the POP3 server All spam must first pass through SMTP server and be delivered to user s mailbox Can result in increased costs Storage, transmission, backup, deletion Third-party entity contracted to filter spam All directed to third-party s remote spam filter cleansed before being redirected to organization Security+ Guide to Network Security Fundamentals, Fourth Edition 31

32 Figure 6-8 Spam filter on POP3 server Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 32

33 Network Security Hardware (cont d.) Virtual private network (VPN) Uses unsecured network as if it were secure All data transmitted between remote device and network is encrypted Types of VPNs Remote-access User to LAN connection Site-to-site Multiple sites can connect to other sites over the Internet Security+ Guide to Network Security Fundamentals, Fourth Edition 33

34 Network Security Hardware (cont d.) Endpoints Used in communicating VPN transmissions May be software on local computer May be VPN concentrator (hardware device) May be integrated into another networking device VPNs can be software-based or hardware-based Hardware-based generally have better security Software-based have more flexibility in managing network traffic Security+ Guide to Network Security Fundamentals, Fourth Edition 34

35 Network Security Hardware (cont d.) Internet content filters Monitor Internet traffic Block access to preselected Web sites and files Unapproved sites identified by URL or matching keywords Security+ Guide to Network Security Fundamentals, Fourth Edition 35

36 Table 6-4 Internet content filter features Security+ Guide to Network Security Fundamentals, Fourth Edition 36

37 Network Security Hardware (cont d.) Web security gateways Can block malicious content in real time Block content through application level filtering Examples of blocked Web traffic ActiveX objects Adware, spyware Peer to peer file sharing Script exploits Security+ Guide to Network Security Fundamentals, Fourth Edition 37

38 Network Security Hardware (cont d.) Passive and active security can be used in a network Active measures provide higher level of security Passive measures Firewall Internet content filter Intrusion detection system (IDS) Active security measure Can detect attack as it occurs Security+ Guide to Network Security Fundamentals, Fourth Edition 38

39 Network Security Hardware (cont d.) Monitoring methodologies Anomaly-based monitoring Compares current detected behavior with baseline Signature-based monitoring Looks for well-known attack signature patterns Behavior-based monitoring Detects abnormal actions by processes or programs Alerts user who decides whether to allow or block activity Heuristic monitoring Uses experience-based techniques Security+ Guide to Network Security Fundamentals, Fourth Edition 39

40 Table 6-5 Methodology comparisons to trap port-scanning application Security+ Guide to Network Security Fundamentals, Fourth Edition 40

41 Network Security Hardware (cont d.) Host intrusion detection system (HIDS) Software-based application that can detect attack as it occurs Installed on each system needing protection Monitors system calls and file system access Can recognize unauthorized Registry modification Monitors all input and output communications Detects anomalous activity Security+ Guide to Network Security Fundamentals, Fourth Edition 41

42 Network Security Hardware (cont d.) Disadvantages of HIDS Cannot monitor network traffic that does not reach local system All log data is stored locally Resource-intensive and can slow system Security+ Guide to Network Security Fundamentals, Fourth Edition 42

43 Network Security Hardware (cont d.) Network intrusion detection system (NIDS) Watches for attacks on the network NIDS sensors installed on firewalls and routers: Gather information and report back to central device Passive NIDS will sound an alarm Active NIDS will sound alarm and take action Actions may include filtering out intruder s IP address or terminating TCP session Security+ Guide to Network Security Fundamentals, Fourth Edition 43

44 Table 6-6 NIDS evaluation techniques Security+ Guide to Network Security Fundamentals, Fourth Edition 44

45 Network Security Hardware (cont d.) Network intrusion prevention system (NIPS) Similar to active NIDS Monitors network traffic to immediately block a malicious attack NIPS sensors located in line on firewall itself Security+ Guide to Network Security Fundamentals, Fourth Edition 45

46 Network Security Hardware (cont d.) All-in-one network security appliances One integrated device replaces multiple security devices Recent trend: Combining multipurpose security appliances with traditional device such as a router Advantage of approach Network devices already process all packets Switch that contains anti-malware software can inspect all packets Security+ Guide to Network Security Fundamentals, Fourth Edition 46

47 Security Through Network Technologies Internet routers normally drop packet with a private address Network address translation (NAT) Allows private IP addresses to be used on the public Internet Replaces private IP address with public address Port address translation (PAT) Variation of NAT Outgoing packets given same IP address but different TCP port number Security+ Guide to Network Security Fundamentals, Fourth Edition 47

48 Table 6-7 Private IP addresses Figure 6-9 Network address translation (NAT) Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 48

49 Security Through Network Advantages of NAT Technologies (cont d.) Masks IP addresses of internal devices Allows multiple devices to share smaller number of public IP addresses Network access control Examines current state of system or network device: Before allowing network connection Device must meet set of criteria If not met, NAC allows connection to quarantine network until deficiencies corrected Security+ Guide to Network Security Fundamentals, Fourth Edition 49

50 Figure 6-10 Network access control framework Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 50

51 Security Through Network Design Elements Elements of a secure network design Demilitarized zones Subnetting Virtual LANs Remote access Security+ Guide to Network Security Fundamentals, Fourth Edition 51

52 Demilitarized Zone (DMZ) Separate network located outside secure network perimeter Untrusted outside users can access DMZ but not secure network Security+ Guide to Network Security Fundamentals, Fourth Edition 52

53 Figure 6-11 DMZ with one firewall Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 53

54 Figure 6-12 DMZ with two firewalls Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 54

55 Subnetting IP address may be split anywhere within its 32 bits Network can be divided into three parts Network Subnet Host Each network can contain several subnets Each subnet can contain multiple hosts Security+ Guide to Network Security Fundamentals, Fourth Edition 55

56 Subnetting (cont d.) Improves network security by isolating groups of hosts Allows administrators to hide internal network layout Security+ Guide to Network Security Fundamentals, Fourth Edition 56

57 Table 6-8 Advantages of subnetting Security+ Guide to Network Security Fundamentals, Fourth Edition 57

58 Figure 6-13 Subnets Cengage Learning 2012 Security+ Guide to Network Security Fundamentals, Fourth Edition 58

59 Virtual LANs (VLAN) Allow scattered users to be logically grouped together: Even if attached to different switches Can isolate sensitive data to VLAN members Communication on a VLAN If connected to same switch, switch handles packet transfer Special tagging protocol used for communicating between switches Security+ Guide to Network Security Fundamentals, Fourth Edition 59

60 Remote Access Working away from the office commonplace today Telecommuters Traveling sales representatives Traveling workers Strong security for remote workers must be maintained Transmissions are routed through networks not managed by the organization Provides same functionality as local users Through VPN or dial-up connection Security+ Guide to Network Security Fundamentals, Fourth Edition 60

61 Summary Standard network security devices provide a degree of security Hubs, switches, router, load balancer Hardware devices specifically designed for security give higher protection level Hardware-based firewall, Web application firewall Proxy server intercepts and processes user requests Virtual private network uses unsecured public network and encryption to provide security Security+ Guide to Network Security Fundamentals, Fourth Edition 61

62 Summary (cont d.) Intrusion detection system designed to detect attack as it occurs Network technologies can help secure a network Network address translation Network access control Methods for designing a secure network Demilitarized zones Virtual LANs Security+ Guide to Network Security Fundamentals, Fourth Edition 62