1

Network Security

Lecture 1

Course Overview

http://web.uettaxila.edu.pk/CMS/coeCCNbsSp09/index.asp

Waleed Ejazwaleed.ejaz@uettaxila.edu.pk

2

Overview

Goal of this course Grading Prerequisites Tentative Schedule Security Goals

3

Goal of This Course

Comprehensive course on network security Includes both theory and practice Theory: Cryptography, Hashes, key exchange,

Email Security, Web Security Practice: Hacking and Anti-Hacker techniques Graduate course: (Advanced Topics)

Lot of independent reading and writing Survey paper

4

CERT

Computer emergency response team (CERT) Security is a #1 concern about Internet. Significant industry and government investment in

security

5

Prerequisites

Computer Communication & Networks

6

Prerequisites ISO/OSI reference model TCP/IP protocol stack Full-Duplex vs half-duplex UTP vs Wireless Cyclic Redundancy Check (CRC) CRC Polynomial Ethernet IEEE 802 MAC Addresses Bridging and Routing IEEE 802.11 LAN

7

Prerequisites (contd.) IP Address Subnets Private vs Public Addresses Address Resolution Protocol (ARP) Internet Control Message Protocol (ICMP) Routing - Dijkstra's algorithm Transport Control Protocol (TCP) User Datagram Protocol (UDP) TCP connection setup TCP Checksum Hypertext Transfer Protocol (HTTP)

8

Text Book

Charlie Kaufman, Radia Perlman, and Mike Speciner, "Network Security: Private Communication in a Public World," 2nd Edition, Prentice Hall, 2002, ISBN: 0130460192.

9

Reference Book

Cryptography and Network Security, by William Stallings, Prentice Hall, 4th Edition, 2006

Few topics from this book will be followed during this course. 

All relevant material will be provided as notes or as part of the class slides.

10

Course Outline Course Overview Security Concepts TCP/IP Security Attacks Security Key Cryptography (Chapter 3) Modes of Operation (Chapter 4) Hashes and Message Digest (Chapter 5) Public Key Cryptography (Chapter 6) Authentication: Passwords, Biometrics (Chapter 10) Kerberos (Chapter 14) Public Key Infrastructure (Chapter 15) IPSec (Chapter 17)

11

Course Outline (contd.) Internet Key Exchange (IKE) (Chapter 18) Web Security: SSL/TLS (Chapter 19) Email Security: PGP (Chapter 22) Firewalls (Chapter 23) VPNs DNS Security Network Access Controls: AAA Wireless Security Intrusion Detection DMZ (LAN->WAN)

12

Grading

Assignments 0% Quizzes 15% Research Paper 15% MID 20% Final Exam 50%

13

Term Project

A survey paper on a network security topic Wireless Network Security Key Exchange Protocols Comprehensive Survey: Technical Papers, Industry

Standards, Products A real attack and protection exercise on the security of a system

(web server, Mail server, …) – Groups of 2 students(Hacker and Administrator)

Recent Developments: Last 5 to 10 years Not in books⇒ Better ones may be submitted to magazines or journals

14

Project Schedule

Week 3: Topic Selection/Proposal Week 6: References Due Week 9: Outline Due Week 13: First Draft/Demo Due Week 16: Final Report Due

15

Office Hours

Monday: 1:00 PM to 3:00 PM Office: Room 9 Contact Office: +92-51-9047573 Best way to communicate with me in other then

office hours is email:

waleed.ejaz@uettaxila.edu.pk Do mention MSc Student in Subject Field

16

FAQs

Yes, I do use “curve”. Your grade depends upon the performance of the rest of the class.

All exams are closed-book and extremely time limited. Exams consist of numerical and may be multiple-choice

(truefalse) questions.

17

Quiz 0: Prerequisites True or False?1. Subnet mask of 255.255.255.254 will allow 254 nodes on the

LAN.2. Time to live (TTL) of 8 means that the packet can travel at most 8

hops.3. IP Address 128.256.210.12 is an invalid IP address4. CRC Polynomial x32+x15+1 will produce a 32 bit CRC.5. DHCP server is required for dynamic IP address assignment6. DNS helps translate an name to MAC address7. Port 80 is used for FTP.8. IPv6 addresses are 32 bits long.9. New connection setup message in TCP contains a syn flag.10. 192.168.0.1 is a public address. Marks = Correct Answers _____ - Incorrect Answers _____ =

______

18

Quiz 0: Prerequisites (Solution) True or False?

1. Subnet mask of 255.255.255.254 will allow 254 nodes on the LAN. False

2. Time to live (TTL) of 8 means that the packet can travel at most 8 hops. True

3. IP Address 128.256.210.12 is an invalid IP address. True4. CRC Polynomial x32+x15+1 will produce a 32 bit CRC. True5. DHCP server is required for dynamic IP address assignment. True6. DNS helps translate an name to MAC address. False7. Port 80 is used for FTP. False8. IPv6 addresses are 32 bits long. False9. New connection setup message in TCP contains a syn flag. True10. 192.168.0.1 is a public address. False Marks = Correct Answers _____ - Incorrect Answers _____ =

______

19

Network Security

Lecture 1

TCP/IP Security Attacks

http://web.uettaxila.edu.pk/CMS/coeCCNbsSp09/index.asp

Waleed Ejazwaleed.ejaz@uettaxila.edu.pk

20

Overview

TCP Segment Format, Connection Setup, Disconnect IP: Address Spoofing, Covert Channel, Fragment Attacks, ARP, DNS TCP Flags: Syn Flood, Ping of Death, Smurf, Fin UDP Flood Attack Connection Hijacking Application: E-Mail, Web spoofing

Ref: Gert De Laet and Gert Schauwers, “Network Security Fundamentals,” Cisco Press, 2005, ISBN:1587051672

21

Security Goals

Security Goals Confidentiality: Need access control,

Cryptography, Existence of data Integrity: No change, content, source, prevention

mechanisms, detection mechanisms Availability: Denial of service attacks,

Confidentiality, Integrity and Availability (CIA)

22

Security Attacks

Security Attacks

Snooping

Traffic Analysis

Modification

Masquerading

Replaying

Repudiation

Traffic Analysis

Snooping

Traffic Analysis

Snooping

Traffic Analysis

Snooping

Traffic Analysis

Snooping

Traffic Analysis

Snooping

Traffic Analysis

Security Attacks

Snooping

Traffic Analysis

Security Attacks

Snooping

Traffic Analysis

Security Attacks

Snooping

Traffic Analysis

Security Attacks

Snooping

Traffic Analysis

Modification

Security Attacks

Snooping

Traffic Analysis Masquerading

Modification

Security Attacks

Snooping

Traffic Analysis

Replaying

Masquerading

Modification

Security Attacks

Snooping

Traffic Analysis

Threat to Confidentiality

Threat to Availability

Threat to Integrity

Denial of Service

23

Passive Versus Active Attacks

Alice and Bob want to communicate in presence of adversaries Adversaries:

Passive – just looking Active – may change msgs

AliceAlice

BobBob

24

Categorization of passive and active attacks

Attacks Passive/Active Threatening

Snooping

Traffic Analysis

Passive Confidentiality

Modification

Masquerading

Replaying

Repudiation

Active Integrity

Denial of Service Active Availability

25

TCP segment format20 to 60 Byte header

26

Connection establishment using three-way handshaking A SYN segment

cannot carry data, but it consumes one sequence number.

A SYN + ACK segment cannot carry data, but does consume one sequence number.

An ACK segment, if carrying no data, consumes no sequence number.

27

Connection termination using three-way handshaking The FIN segment

consumes one sequence number if it does not carry data.

The FIN + ACK segment consumes one sequence number if it does not carry data.

28

IP address Spoofing Send requests to server with someone X's IP

address. The response is received at X and discarded. Both X and server can be kept busy DoS attack⇒

29

TCP Flags

Invalid combinations

May cause recipient to crash or hang

30

Syn Flood A sends Syn request with IP address of X to Server

V. V sends a syn+ack to X X discards syn+ack leaving an half open connection

at V. Many open connections exhausts resources at V ⇒

DoS

31

Ping of Death

Send a ping with more than 64kB in the data field.

Most systems would crash, hang or reboot.

32

Smurf

Send a broadcast echo request with the V's source address.

All the echo replies will make V very busy.

33

Fin

In the middle of conversation between X and V.

H sends a packet with Fin flag to V. V closes the connection and disregards all

further packets from X. RST flag can be used similarly

34

Connection Hijacking H sends packets to server X which increments

the sequence number at X. All further packets from V are discarded at X. Responses for packets from H are sent to V -

confusing him.

35

Address Resolution Protocol

36

ARP: Address Resolution Protocol Mapping from IP addresses to MAC addresses

Request

192.168.0

.1 .2 .3 .4 .508:00:20:03:F6:42 00:00:C0:C2:9B:26

Reply

192.168.0

.1 .2 .3 .4 .508:00:20:03:F6:42 00:00:C0:C2:9B:26

arp req | target IP: 192.168.0.5 | target eth: ?

arp rep | sender IP: 192.168.0.5 | sender eth: 00:00:C0:C2:9B:26

37

ARP Spoofing X tries to find the MAC address of Victim V Hacker H responds to ARP request

pretending to be V. All communication for V is captured by H. Countermeasure: Use static ARP

38

DNS Spoofing

DNS server is compromised to provide H's IP address for V's name.

Countermeasure

39

Email Spoofing From address is spoofed. Malware attachment comes from a friendly

address. From: God@heavens.com

40

Web Spoofing

The web site looks like another Southwest Airline,

http://airlines.ws/southwest-airline.htm For every .gov site there is a .com, .net giving

similar information For misspellings of popular businesses, there

are web sites.

41

Summary1. TCP port numbers, Sequence numbers, ack, flags2. IP addresses are easy to spoof. ARP and DNS are

not secure.3. Flags: Syn Flood, Ping of Death, Smurf, Fin,

Connection Hijacking4. UDP Flood Attack5. Application addresses are not secure

42

References

1. Gert De Laet and Gert Schauwers, “Network Security Fundamentals,” Cisco Press, 2005, ISBN:1587051672

43

Lab Home Work 1: Gathering Information

Learn about IPconfig, ping, arp, nslookup, whois, tracert, netstat, route, hosts file 1. Find the IP addresses of www.google.com 2. Modify the hosts file to map www.google.com to 128.252.166.33 and do a

google search. Remove the modification to the host file and repeat. 3. Find the domain name of 128.272.165.7 (reverse the address and

add .inaddr. arpa) 4. Find the owner of www.google.com domain 5. Find route from your computer to www.google.com 6. Find the MAC address of your computer 7. Print your ARP cache table. Find a server on your local network. Change its

ARP entry in your computer to point to your computer’s MAC address. Print new ARP cache table. Now use the service and see what happens.

8. Print your routing table and explain each line (up to line #20 if too many) 9. What is the number of packets sent with “destination unreachable” 10. Find the location of 128.252.166.33 (use www.ipaddresslocation.org)

44

Questions!