Ip spoofingine xbnxnxnxnxnxnx xxhdbhdbdjdhxjxjxjjxjxjxjxj

1. IP Spoofing, CS265 1
IP Spoofing
Bao Ho
ToanTai Vu
CS 265 - Security Engineering
Spring 2003
San Jose State University

2. IP Spoofing, CS265 2
Presentation Outline
 Introduction, Background
 Attacks with IP Spoofing
 Counter Measures
 Summary

3. IP Spoofing, CS265 3
IP Spoofing
 IP Spoofing is a technique used to gain unauthorized
access to computers.
– IP: Internet Protocol
– Spoofing: using somebdody else’s information
 Exploits the trust relationships
 Intruder sends messages to a computer with an IP
address of a trusted host.

4. IP Spoofing, CS265 4
IP / TCP
 IP is connectionless, unreliable
 TCP connection-oriented
TCP/IP handshake
A  B: SYN; my number is X
B  A: ACK; now X+1
SYN; my number is Y
A B: ACK; now Y+1

5. IP Spoofing, CS265 5
A blind Attack
Host I cannot see what Host V send back

6. IP Spoofing, CS265 6
IP Spoofing Steps
 Selecting a target host (the victim)
 Identify a host that the target “trust”
 Disable the trusted host, sampled the target’s TCP
sequence
 The trusted host is impersonated and the ISN forged.
 Connection attempt to a service that only requires
address-based authentication.
 If successfully connected, executes a simple
command to leave a backdoor.

7. IP Spoofing, CS265 7
IP Spoofing Attacks
 Man in the middle
 Routing
 Flooding / Smurfing

8. IP Spoofing, CS265 8
Attacks
Man - in - the - middle:
Packet sniffs on link between the two endpoints, and
therefore can pretend to be one end of the
connection.

9. IP Spoofing, CS265 9
Attacks
 Routing re-direct: redirects routing information
from the original host to the attacker’s host.
 Source routing: The attacker redirects individual
packets by the hacker’s host.

10. IP Spoofing, CS265 10
Attacks
 Flooding: SYN flood fills up the receive queue from
random source addresses.
 Smurfing: ICMP packet spoofed to originate from the
victim, destined for the broadcast address, causing all
hosts on the network to respond to the victim at
once.

11. IP Spoofing, CS265 11
IP-Spoofing Facts
 IP protocol is inherently weak
 Makes no assumption about sender/recipient
 Nodes on path do not check sender’s identity
 There is no way to completely eliminate IP spoofing
 Can only reduce the possibility of attack

12. IP Spoofing, CS265 12
IP-Spoofing
Counter-measures
 No insecure authenticated services
 Disable commands like ping
 Use encryption
 Strengthen TCP/IP protocol
 Firewall
 IP traceback

13. IP Spoofing, CS265 13
No insecure authenticated
services
 r* services are hostname-based or IP-based
 Other more secure alternatives, i.e., ssh
 Remove binary files
 Disable in inet, xinet
 Clean up .rhost files and /etc/host.equiv
 No application with hostname/IP-based
authentication, if possible

14. IP Spoofing, CS265 14
Disable ping command
 ping command has rare use
 Can be used to trigger a DOS attack by flooding the
victim with ICMP packets
 This attack does not crash victim, but consume
network bandwidth and system resources
 Victim fails to provide other services, and halts if runs
out of memory

15. IP Spoofing, CS265 15
DOS using Ping

16. IP Spoofing, CS265 16
Use Encryption
 Encrypt traffic, especially TCP/IP packets and Initial
Sequence Numbers
 Kerberos is free, and is built-in with OS
 Limit session time
 Digital signature can be used to identify the sender of
the TCP/IP packet.

17. IP Spoofing, CS265 17
Strengthen TCP/IP protocol
 Use good random number generators to generate
ISN
 Shorten time-out value in TCP/IP request
 Increase request queue size
 Cannot completely prevent TCP/IP half-open-
connection attack
 Can only buy more time, in hope that the attack will
be noticed.

18. IP Spoofing, CS265 18
Firewall
 Limit traffic to services that are offered
 Control access from within the network
 Free software: ipchains, iptables
 Commercial firewall software
 Packet filters: router with firewall built-in
 Multiple layer of firewall

19. IP Spoofing, CS265 19
Network layout with Firewall

20. IP Spoofing, CS265 20
IP Trace-back
 To trace back as close to the attacker’s location as
possible
 Limited in reliability and efficiency
 Require cooperation of many other network operators
along the routing path
 Generally does not receive much attention from
network operators

21. IP Spoofing, CS265 21
Summary/Conclusion
 IP spoofing attacks is unavoidable.
 Understanding how and why spoofing attacks are
used, combined with a few simple prevention
methods, can help protect your network from these
malicious cloaking and cracking techniques.

22. IP Spoofing, CS265 22
References
 IP-spoofing Demystified (Trust-Relationship Exploitation), Phrack Magazine Review, Vol. 7, No. 48, pp. 48-
14, www.networkcommand.com/docs/ipspoof.txt
 Security Enginerring: A Guide to Building Dependable Distributed Systems, Ross Anderson, pp. 371
 Introduction to IP Spoofing, Victor Velasco, November 21, 2000,
www.sans.org/rr/threats/intro_spoofing.php
 A Large-scale Distributed Intrusion Detection Framework Based on Attack Strategy Analysis, Ming-Yuh
Huang, Thomas M. Wicks, Applied Research and Technology, The Boeing Company
 Internet Vulnerabilities Related to TCP/IP and T/TCP, ACM SIGCOMM, Computer Communication Review
 IP Spoofing, www.linuxgazette.com/issue63/sharma.html
 Distributed System: Concepts and Design, Chapter 7, by Coulouris, Dollimore, and Kindberg
 FreeBSD IP Spoofing, www.securityfocus.com/advisories/2703
 IP Spoofing Attacks and Hijacked Terminal Connections, www.cert.org/advisories/CA-1995-01.html
 Network support for IP trace-back, IEEE/ACM Transactions on Networking, Vol. 9, No. 3, June 2001
 An Algebraic Approach to IP Trace-back, ACM Transactions on Information and System Security, Vol. 5, No.
2, May 2002
 Web Spoofing. An Internet Con Game, http://bau2.uibk.ac.at/matic/spoofing.htm

23. IP Spoofing, CS265 23
Questions / Answers