TCP/IP Vulnerabilities

1. TCP/IP Vulnerabilities

2. Internet design goals • Interconnection • Failure resilience • Multiple types of service • Variety of networks • Management of resources • Cost-effective • Low entry-cost • Accountability for resources Where is security issues?

3. Why did they leave it out? • Designed for simple connectivity • Network designed with implicit trust • No “bad” guys • Security may be provided at the edge • Encryption • Authentication

4. Security Vulnerabilities • Unfortunately at every layer in the protocol stack! • Network-layer attacks • IP-level vulnerabilities • Routing attacks • Transport-layer attacks • TCP vulnerabilities • Application-layer attacks

5. Where do the problems come from? • Protocol-level vulnerabilities • Implicit trust assumptions in design • Implementation vulnerabilities • Both on routers and end-hosts • Incomplete specifications • Often left to the imagination of programmers

6. IP-level vulnerabilities • IP addresses are provided by the source • Spoofing attacks • Use of IP address for authentication • Remote command (rsh, rlogin) allows remote login without explicit password authentication • Some known exploited IP • Fragmentation • Traffic amplification

7. Routing attacks • Divert traffic to malicious nodes • Black-hole attack • Eavesdropping • Routing attacks • No authentications • Announce lower cost route in Distance-Vector • BGP vulnerabilities • Prefix hijacking

8. TCP-level attacks • SYN-Flooding • Flood with incomplete connection to hold service resources • Session hijack • Sequence number guessing • Pretend to be a trusted host • Session Termination • Forge packet to close a legitimate connection

9. Application Vulnerabilities • Application Protocol Attack • SPAM • Phishing • etc.

10. Outline • Security Vulnerabilities • Denial of Service • Worms • Countermeasures: Firewalls/IDS

11. Denial of Service • Make a service unusable by overloading the server or network • Disrupt service by taking down hosts • e.g., ping-of-death • Consume host-level resources • e.g., SYN-floods • Consume network resources • e.g., UDP/ICMP floods

12. Outline • Security Vulnerabilities • Denial of Service • Worms • Countermeasures: Firewalls/IDS

13. Worm Overview • Self-propagate through network • Typical Steps in Worm Propagation • Probe host for vulnerable software • Exploit the vulnerability • Launches copy of itself on compromised host • Very fast spreading with short windows to react

14. Worm • Not attached but spreads by itself • Exploit system vulnerability like buffer overflow or flawed protocol • Consume system resources • Modify system configurations • Typical Steps in Worm Propagation • Probe host for vulnerable software • Exploit the vulnerability • Launches copy of itself on compromised host

15. The Case of Code-Red • 12th July 2001 : Code-Red Worm (CRv1) began • 19th July 2001 : Code-Red Worm (CRv2) began • 359,104 hosts were compromised in approximately 24 hours The total number of inactive hosts over time The number of newly inactive hosts per minute http://www.caida.org/analysis/security/code-red/coderedv2_analysis.xml Worm growth: Slow-start, Exponential phase, Slow decay

16. Code Red Spreads (I) July 19, Midnight – 159 hosts infected

17. Code Red Spreads (II) July 19, 11:40 am – 4,920 hosts infected

18. Code Red Spreads (III) July 20, Midnight – 341,015 hosts infected

19. Animation of Code Red Spreads

20. Animation SQL Slammer Spreads

21. Outline • Security, Vulnerabilities • Denial of Service • Worms • Countermeasures: Firewalls/IDS

22. Firewall • A Firewall is a system or group of systems used to control access between two networks using pre-configured rules or filters

23. How to filter? • What to filter based on? • Packet Header Fields • IP source and destination addresses • Application port numbers • ICMP message types/ Protocol options etc. • Packet contents (payloads)

24. Some examples • Block all packets from outside except for SMTP servers • Block all traffic to/from a list of domains • Ingress filtering • Drop all packets from outside with addresses inside the network • Egress filtering • Drop all packets from inside with addresses outside the network

25. Typical Firewall Configuration Internet • Internal hosts can access DMZ and Internet • External hosts can access DMZ only, not Intranet • DMZ hosts can access Internet only • Advantages? • If a service gets compromised in DMZ it cannot affect internal hosts DMZ X X Intranet

26. Client Server SYN SYN/ACK ACK SSH-1 In Ext > 1023 Int 22 TCP Any Allow SSH-2 Out Int 22 Ext > 1023 TCP Yes Alow Sample Firewall Rule • Allow SSH from external hosts to internal hosts • Two rules • Inbound and outbound • How to know a packet is for SSH? • Inbound: src-port>1023, dst-port=22 • Outbound: src-port=22, dst-port>1023 • Protocol=TCP • Ack Set? Rule Dir Src Addr Src Port Dst Addr Dst Port Proto Ack Set? Action

27. Intrusion Detection • IDS is an automated system intended to detect computer intrusions • To identify, preferably in real-time, unauthorized use, misuse, and abuse of computer system

28. Basic IDS Architecture

29. Detection Method • Misuse Detection • Looking for the attempts to exploit known vulnerabilities or attack patterns • Typically low false alarms • Difficult to gather all attack signatures • Anomaly Detection • Observing a deviation of normal behavior of system or user to detect intrusions • Can detect a new or unseen vulnerabilities or attack patterns • Typically a lot of false alarms

30. Audit Source Location Host/IDS Host Host Host based IDS IDS Host Host Network based IDS

31. Summary • Security vulnerabilities are real! • Protocol or implementation or bad specs • Poor programming practices • At all layers in protocol stack • DoS/DDoS • Resource utilization • Worm • Exponential spread • Scanning strategies • Firewall/IDS • Counter-measures to protect hosts • Fail-open vs. Fail-close?