1. Lecture 24 Secure Communications CS 450/650 Fundamentals of Integrated Computer Security Slides are modified from Ian Goldberg

2. Who Attacks Networks Hackers break into organizations from the outside – Challenge – Fame – Money & Espionage – Ideology However, most security breaches are internal, by employees and ex-employees 22 CS 450/650 – Lecture 24: Secure Communications

3. Threat Precursors Port Scan Social Engineering – Reconnaissance – Bulletin Board / Chat – Docs Packet Sniffers (telnet/ftp in cleartext) 33 CS 450/650 – Lecture 24: Secure Communications

4. Network Security Threats Interception – If interceptor cannot read, have confidentiality (privacy) – If cannot modify without detection, have message integrity 44 CS 450/650 – Lecture 24: Secure Communications

5. Network Security Threats Impostors (Spoofing/ Masquerade) – Claim to be someone else – Need to authenticate the sender--prove that they are who they claim to be True Person Impostor 55 CS 450/650 – Lecture 24: Secure Communications

6. Network Security Threats Remotely Log in as Root User – Requires cracking the root login password – Then control the machine – Read and/or steal information – Damage data (erase hard disk) – Create backdoor user account that will let them in easily later Root Login Command 66 CS 450/650 – Lecture 24: Secure Communications

7. Security Threats Content Threats – Application layer content may cause problems Viruses In many ways, most severe security problem in corporations today Must examine application messages 77 CS 450/650 – Lecture 24: Secure Communications

8. Replay Attack First, attacker intercepts a message – Not difficult to do 88 CS 450/650 – Lecture 24: Secure Communications

9. Replay Attack Later, attacker retransmits (replays) the message to the original destination host – Does not have to be able to read a message to replay it 99 CS 450/650 – Lecture 24: Secure Communications

10. Replay Attack Why replay attacks? – To gain access to resources by replaying an authentication message – In a denial-of-service attack, to confuse the destination host 10 CS 450/650 – Lecture 24: Secure Communications

11. Thwarting Replay Attacks Put a time stamp in each message to ensure that the message is “fresh” – Do not accept a message that is too old Place a sequence number in each message – Do not accept a duplicated message Message Sequence Number Time Stamp 11 CS 450/650 – Lecture 24: Secure Communications

12. Thwarting Replay Attacks In request-response applications, – Sender of request generates a nonce (random number) – Places the nonce in the request – Server places the nonce in the response – Neither party accepts duplicate nonces Nonce RequestResponse 12 CS 450/650 – Lecture 24: Secure Communications

13. Network Security Threats Denial of Service (DOS) Attacks – Overload system with a flood of messages – Or, send a single message that crashes the machine 13 CS 450/650 – Lecture 24: Secure Communications

14. Denial of Service (DOS) Attacks Transmission Failure Connection Flooding – Echo-Chargen – Ping of Death – Smurf – Syn Flood – Traffic Redirection – DNS Attacks Distributed Denial of Service 14 CS 450/650 – Lecture 24: Secure Communications

15. SSL Integrated Security System SSL – Secure Sockets Layer – Developed by Netscape TLS (now) – Netscape gave IETF control over SSL – IETF renamed it TLS (Transport Layer Security) – Usually still called SSL 15 CS 450/650 – Lecture 24: Secure Communications

16. Location of SSL Below the Application Layer – IETF views it at the transport layer – Protects all application exchanges – Not limited to any single application WWW transactions, e-mail, etc. SSL E-MailWWWE-MailWWW 16 CS 450/650 – Lecture 24: Secure Communications

17. SSL Operation Browser & Webserver Software Implement SSL – User can be unaware 17 CS 450/650 – Lecture 24: Secure Communications

18. SSL Operation SSL ISS Process – Two sides negotiate security parameters – Webserver authenticates itself – Browser may authenticate itself but rarely does – Browser selects a symmetric session key, sends to webserver – Adds a digital signature and encrypts all messages with the symmetric key 18 CS 450/650 – Lecture 24: Secure Communications

19. Importance of SSL Supported by Almost All Browsers – De facto standard for Internet application security Problems – Relatively weak security – Does not involve security on merchant server – Does not validate credit card numbers – Viewed as an available but temporary approach to consumer security 19 CS 450/650 – Lecture 24: Secure Communications

20. Other ISSs SSL is merely an example integrated security system Many other ISSs exist – IPsec – PPP and PPTP – Etc. 20 CS 450/650 – Lecture 24: Secure Communications

21. Other ISSs All ISSs have the same general steps – Negotiate security parameters – Authenticate the partners – Exchange a session key – Communicate with message-by-message privacy, authentication, and message integrity 21 CS 450/650 – Lecture 24: Secure Communications

22. VPNs IETF developing IPsec security standards – IP security – At the internet layer – Protects all messages at the transport and application layers IPsec TCPUDP E-Mail, WWW, Database, etc. 22 CS 450/650 – Lecture 24: Secure Communications

23. VPNs IPsec Transport Mode – End-to-end security for hosts Local Network Internet Local Network Secure Communication 23 CS 450/650 – Lecture 24: Secure Communications

24. VPNs IPsec Tunnel Mode – IPsec server at each site – Secure communication between sites Local Network Internet Local Network Secure Communication IPsec Server 24 CS 450/650 – Lecture 24: Secure Communications

25. VPNs IPsec Modes Can be Combined – End-to-end transport mode connection – Within site-to-site tunnel connection Local Network Internet Local Network Tunnel Mode Transport Mode 25 CS 450/650 – Lecture 24: Secure Communications

26. VPNs Another Security System for VPNs is the Point- to-Point Tunneling Protocol (PPTP) – For dial-up connections, based on PPP – Connects user with securely to a remote access server at a site Internet Local Network Remote Access Server Dial-Up Connection PPTP Connection 26 CS 450/650 – Lecture 24: Secure Communications

27. IPsec IPsec (IP security) Security for transmission over IP networks – The Internet – Internal corporate IP networks – IP packets sent over public switched data networks (PSDN) Local Network Internet Local Network 27 CS 450/650 – Lecture 24: Secure Communications

28. IPsec Why do we need IPsec? – IP has no security – Add security to create a virtual private network (VPN) to give secure communication over the Internet or another IP network Local Network Internet Local Network 28 CS 450/650 – Lecture 24: Secure Communications

29. IPsec Genesis – Being created by the Internet Engineering Task Force – For both IP version 4 and IP version 6 29 CS 450/650 – Lecture 24: Secure Communications

30. IPsec Two Modes of operation Tunnel Mode – IPsec server at each site – Secures messages going through the Internet Local Network Internet Local Network Secure Communication IPsec Server 30 CS 450/650 – Lecture 24: Secure Communications

31. IPsec Tunnel Mode – Hosts operate in their usual way Tunnel mode IPsec is transparent to the hosts – No security within the site networks Local Network Internet Local Network Secure Communication IPsec Server 31 CS 450/650 – Lecture 24: Secure Communications

32. IPsec Two Modes of operation Transport Mode – End-to-end security between the hosts – Security within site networks as well – Requires hosts to implement IPsec Local Network Internet Local Network Secure Communication 32 CS 450/650 – Lecture 24: Secure Communications

33. IPsec Transport Mode – Adds a security header to IP packet – After the main IP header – Source and destination addresses of hosts can be learned by interceptor – Only the original data field is protected Protected Original Data Field Original IP Header Transport Security Header 33 CS 450/650 – Lecture 24: Secure Communications

34. IPsec Tunnel Mode – Adds a security header before the original IP header – Has IP addresses of the source and destination IPsec servers only, not those of the source and destination hosts – Protects the main IP header Protected Original Data Field Protected Original IP Header Tunnel Security Header 34 CS 450/650 – Lecture 24: Secure Communications

35. IPsec Can combine the two modes – Transport mode for end-to-end security – Plus tunnel mode to hide the IP addresses of the source and destination hosts during passage through the Internet Local Network Internet Local Network Tunnel Mode Transport Mode 35 CS 450/650 – Lecture 24: Secure Communications

36. IPsec Two forms of protection Encapsulating Security Protocol (ESP) security provides confidentiality as well as authentication Authentication Header (AH) security provides authentication but not confidentiality – Useful where encryption is forbidden by law – Provides slightly better authentication by providing authentication over a slightly larger part of the message, but this is rarely decisive 36 CS 450/650 – Lecture 24: Secure Communications

37. IPsec Modes and protection methods can be applied in any combination Tunnel Mode Transport Mode ESPSupportedSupported AHSupportedSupported 37 CS 450/650 – Lecture 24: Secure Communications

38. 38 CS 450/650 – Lecture 24: Secure Communications IPsec Security Associations (SAs) are agreements between two hosts or two IPsec servers, depending on the mode “Contracts” for how security will be performed Negotiated Governs subsequent transmissions Host AHost B Negotiate Security Association

39. IPsec Security Associations (SAs) can be asymmetrical – Different strengths in the two directions – For instance, clients and servers may have different security needs Host AHost B SA for messages From A to B SA for messages From B to A 39 CS 450/650 – Lecture 24: Secure Communications

40. IPsec Policies may limit what SAs can be negotiated – To ensure that adequately strong SAs for the organization’s threats – Gives uniformity to negotiation decisions Host AHost B Security Association Negotiations Limited By Policies 40 CS 450/650 – Lecture 24: Secure Communications

41. IPsec First, two parties negotiate IKE (Internet Key Exchange) Security Associations – IKE is not IPsec-specific – Can be used in other security protocols Host AHost B Communication Governed by IKE SA 41 CS 450/650 – Lecture 24: Secure Communications

42. IPsec Under the protection of communication governed by this IKE SA, negotiate IPsec- specific security associations Host AHost B Communication Governed by IKE SA IPsec SA Negotiation 42 CS 450/650 – Lecture 24: Secure Communications

43. IPsec Process of Creating IKE SAs (and other SAs) – Negotiate security parameters within policy limitations – Authenticate the parties using SA-agreed methods – Exchange a symmetric session key using SA-agreed method – Communicate securely with confidentiality, message-by-message authentication, and message integrity using SA-agreed method 43 CS 450/650 – Lecture 24: Secure Communications

44. IPsec IPsec has mandatory security algorithms – Uses them as defaults if no other algorithm is negotiated – Other algorithms may be negotiated – But these mandatory algorithms MUST be supported 44 CS 450/650 – Lecture 24: Secure Communications

45. PKIs To use public key methods, an organization must establish a comprehensive Public Key Infrastructure (PKI) – A PKI automates most aspects of using public key encryption and authentication – Uses a PKI Server PKI Server 45 CS 450/650 – Lecture 24: Secure Communications

46. PKIs PKI Server Creates Public Key-Private Key Pairs – Distributes private keys to applicants securely – Often, private keys are embedded in delivered software PKI Server Private Key 46 CS 450/650 – Lecture 24: Secure Communications

47. PKIs PKI Server Provides CRL Checks – Distributes digital certificates to verifiers – Checks certificate revocation list before sending digital certificates PKI Server Digital Certificate 47 CS 450/650 – Lecture 24: Secure Communications

48. PKIs CRL (Certificate Revocation List) Checks – If applicant gives verifier a digital certificate, – The verifier must check the certificate revocation list PKI Server OK? OK or Revoked CRL 48 CS 450/650 – Lecture 24: Secure Communications

49. Integrated Security System When two parties communicate … – Their software usually handles the details – First, negotiate security methods – Then, authenticate one another – Then, exchange symmetric session key – Then can communicate securely using symmetric session key and message-by-message authentication 49 CS 450/650 – Lecture 24: Secure Communications

50. Multi-Layer Security Security Can be Applied at Multiple Layers Simultaneously – Application layer security for database, e-mail, etc. – Transport layer: SSL – Internet layer: IPsec – Data link layer: PPTP, L2TP – Physical layer: locks 50 CS 450/650 – Lecture 24: Secure Communications

51. Multi-Layer Security Applying security at 2 or more layers is good – If security is broken at one layer, the communication will still be secure However, – Security slows down processing – Multi-Layer security slows down processing at each layer 51 CS 450/650 – Lecture 24: Secure Communications

52. Total Security Network Security is Only Part Server Security – Hackers can take down servers with denial-of- service attack – Hacker can log in as root user and take over the server – Steal data, lock out legitimate users, etc. 52 CS 450/650 – Lecture 24: Secure Communications

53. Total Security Server Security – Occasionally, weakness are discovered in server operating systems – This knowledge is quickly disseminated – Known security weaknesses 53 CS 450/650 – Lecture 24: Secure Communications

54. Total Security Server Security – Server operating system (SOS) vendors create patches – Many firms do not download patches – This makes them vulnerable to hackers, who quickly develop tools to probe for and then exploit known weaknesses 54 CS 450/650 – Lecture 24: Secure Communications

55. Total Security Client PC Security – Known security weaknesses exist but patches are rarely downloaded – Users often have no passwords or weak passwords on their computer – Adversaries take over client PCs and can therefore take over control over SSL, other secure communication protocols 55 CS 450/650 – Lecture 24: Secure Communications

56. Total Security Application Software – May contain viruses Must filter incoming messages – Database and other applications can add their own security with passwords and other protections 56 CS 450/650 – Lecture 24: Secure Communications

57. Total Security Managing Users – Often violate security procedures, making technical security worthless – Social engineering: attacker tricks user into violating security procedures 57 CS 450/650 – Lecture 24: Secure Communications

58. Defense in Depth Firewalls Antivirus Intrusion Detection Systems Intrusion Protection Systems 58 CS 450/650 – Lecture 24: Secure Communications