Datasäkerhet och integritet

Transkript

1 Chapter 4 module A Networking Concepts OSI-modellen TCP/IP This module is a refresher on networking concepts, which are important in information security

2 A Simple Home Network 2

3 Unshielded Twisted Pair Wiring (UTP) Cord 3

4 Building LAN 4

5 Wide Area Networks (WANs) 5

6 The Internet 1 6

7 The Internet 2 The global Internet has thousands of networks connected by routers Browser Network Packet Router Packet Route Router Packet Webserver Software Router 7

8 Frames and Packets Packet travels in a different frame in each network 8

9 Internet Service Providers (ISPs) 9

10 Layered Standards Architectures Super Layer Application Internetworking Network Description Communication between application programs on different hosts attached to different networks on an internet. Transmission of packets across an internet. Packets contain application layer messages. Transmission of frames across a network. Frames contain packets. Super Layer TCP/IP OSI Application Application Internet Transport Internet Subnet Access Application Presentation Session Transport Network Data Link Physical Single Network Hybrid TCP/IPOSI Application Transport Internet Data Link Physical 10

11 TCP/IP overview 11

12 Physical and Data Link Layers In a single network, a physical link connects adjacent devices. A data link is the path that a frame takes across a single network. One data link; three physical links. 12

13 Internet and Transport Layer Standards 13

14 Internet Protocol (IP) Packet IP Version 4 Packet 14

15 IP Version 6 (IPv6) Packet 15

16 Transmission Control Protocol (TCP) Segment 16

17 Messages in a TCP Session 1 PC transport process Open (3) 1. SYN (Open) Webserver transport process 2. SYN, ACK (1) (Acknowledgement of 1) 3. ACK (2) 3-Way Open 17

18 Messages in a TCP Session 2 PC transport process Open (3) Carry HTTP Req & Resp (4) 1. SYN (Open) Webserver transport process 2. SYN, ACK (1) (Acknowledgement of 1) 3. ACK (2) 4. Data = HTTP Request 5. ACK (4) 6. Data = HTTP Response 7. ACK (6) Data exchange 18

19 Messages in a TCP Session 3 PC transport process Carry HTTP Req & Resp (4) Webserver transport process 8. Data = HTTP Request (Error) 9. Data = HTTP Request (No ACK so Retransmit) 10. ACK (9) 11. Data = HTTP Response 12. ACK (11) Error Handling 19

20 Messages in a TCP Session 4 PC transport process Close (4) Normal Four-Way Close Webserver transport process 13. FIN (Close) 14. ACK (13) 15. FIN 16. ACK (15) Note: An ACK may be combined with the next message if the next message is sent quickly enough 20

21 TCP/IP function overview 21

22 Messages in a TCP Session 5 PC transport process Close (1) Abrupt Close Webserver transport process RST Either side can send a Reset (RST) segment at any time Ends the Session Immediately 22

23 TCP Sequence and Acknowledgement Numbers 23

24 Multitasking Server Host and Port Numbers 24

25 Sockets 25

26 User Datagram Protocol (UDP) 26

27 Internet Control Message Protocol (ICMP) 27

28 Domain Name System (DNS) Server 28

29 Dynamic Routing Protocols 29

30 Simple Network Management Protocol (SNMP) 30

31 Application Standards Application Exploits Many Applications Need Two Types of Standards One for the transmission of messages, one for the content of application documents For the World Wide Web, these are HTTP and HTML, respectively For transmission, uses SMTP, POP, and IMAP For message content, uses RFC 2822 (all-text), HTML, and MIME FTP and Telnet By taking over applications, hackers gain the permissions of the exploited program A multitude of application standards Consequently, there is a multitude of security issues at the application level Have no security Passwords are transmitted in the clear, making it possible to be captured by sniffers Secure Shell (SSH) can replace both securely Many Other Application Standards Have Security Issues Voice over IP (VoIP) Service-oriented architecture (SOA); web services Peer-to-peer applications 31