1. Black Hat Europe 2000: Strategies for Defeating Distributed Attacks Simple Nomad Hacker Nomad Mobile Research Centre Occam Theorist RAZOR Security Team, BindView Corporation

2. About Myself  http://www.nmrc.org/ http://www.nmrc.org/  Currently Sr. Security Analyst for BindView’s RAZOR Team, http://razor.bindview.com/ http://razor.bindview.com/

3. About This Presentation  Assume basics –Understand IP addressing –Understand basic system administration  Tools –Where to find them –Basic usage  Terminology  A “Network” point of view

4. Background  Originally developed during early 1999  Concepts first discussed October 1999  Many concepts can be found in DDOS software today

5. Attack Recognition Basics  Pattern Recognition –Examples: Byte sequence in RAM Packet content in a network transmission Half opens against a server within a certain time frame –Considered “real-time”

6. Attack Recognition Basics Cont.  Effect Recognition –Examples Unscheduled server restart in logs Unexplainable CPU utilization System binaries altered –Considered “non” real-time

7. Attack Recognition Problems  Blended “pattern” and “effect” attacks  Sniffing attacks  Decoys and false identification of attack source

8. Attack Recognition Problems Cont.  Current solutions are usually “pattern” or “effect”, no real-time global solutions  Existing large scale solutions can easily be defeated

9. Common Thwarting Techniques  Rule-based systems can be tricked  Log watchers can be deceived  Time-based rules can be bypassed

10. What is Needed  The “Overall Behavior Network/Host Monitoring Tool” (which doesn’t exist)

11. What Do We Do?  “Trickle Down Security” –Solutions for distributed attacks will introduce good security overall  Off-the-shelf is not enough  Learn about attack types  Defensive techniques

12. Changing Attack Patterns  More large-scale attacks  Better enumeration and assessment of the target by the attacker

13. Two Basic Distributed Attack Models  Attacks that do not require direct observation of the results  Attacks that require the attacker to directly observe the results

14. Basic Model ServerAgent Client Issue commands Processes commands to agents Carries out commands

15. More Advanced Model TargetAttacker Forged ICMP Timestamp Requests ICMP Timestamp Replies Sniffed Replies

16. Even More Advanced Model Target Attack Node Sniffed Replies Attack Node FirewallFirewall Upstream Host Attacks or Probes Replies

17. ICMP  Sweeping a network with Echo  Typical alternates to ping –Timestamp –Info Request

18. Fun with ICMP  Advanced ICMP enumeration –ICMP fingerprinting –Invalid header info to enumerate hosts

19. Host Enumeration #./icmpenum -i 2 -c xxx.xx.218.0 xxx.xx.218.23 is up xxx.xx.218.26 is up xxx.xx.218.52 is up xxx.xx.218.53 is up xxx.xx.218.58 is up xxx.xx.218.63 is up xxx.xx.218.82 is up xxx.xx.218.90 is up xxx.xx.218.92 is up xxx.xx.218.96 is up xxx.xx.218.118 is up xxx.xx.218.123 is up xxx.xx.218.126 is up xxx.xx.218.130 is up xxx.xx.218.187 is up xxx.xx.218.189 is up xxx.xx.218.215 is up xxx.xx.218.253 is up

20. Nmap  Ping sweeps  Port scanning  TCP fingerprinting

21. Fun with Nmap  Additional features –“Same segment” sniffing

22. Addition Probes  Possible security devices –Using “bait” to fish out security mechanisms  Sweep for promiscuous devices –False hosts and DNS lookups

23. Network Mapping Sun Linux Firewall NT Hosts InsideDMZ www ftp cw swb VPN Internet Routers Linux 2.0.38 xxx.xx.48.2 AIX 4.2.1 xxx.xx.48.1 Checkpoint Firewall-1 Solaris 2.7 xxx.xx.49.17 Checkpoint Firewall-1 Nortel Extranet xxx.xx.22. 7 Cisco 7206 204.70.xxx.xxx Nortel CVX1800 151.164.x.xxx IDS?

24. Defensive Techniques  Good security policy  Split DNS –All public systems in one DNS server located in DMZ –All internal systems using private addresses with separate DNS server internally  Drop/reject packets with a TTL of 1 or 0

25. Defensive Techniques Cont.  Minimal ports open  Stateful inspection firewalls  Modified kernels/IDS to look for fingerprint packets

26. Defensive Techniques Cont.  Limit ICMP inbound to host/destination unreachable  Limit outbound ICMP

27. DMZ Server Recommendations  Split services between servers  Current patches  Use trusted paths, anti-buffer overflow settings and kernel patches  Use any built-in firewalling software  Make use of built-in state tables

28. Firewall Rules  Limit inbound to only necessary services  Limit outbound via proxies to help control access  Block all outbound to only necessary traffic

29. Intrusion Detection Systems  Use only IDS’s that can be customized  IDS should be capable of handling fragmented packet reassembly  IDS should handle high speeds

30. Spoofed Packet Defenses  Get TTL of suspected spoofed packet  Probe the source address in the packet  Compare the probe reply’s TTL to the suspected spoofed packet

31. Questions, etc.  For followup: –http://razor.bindview.com/http://razor.bindview.com/ –thegnome@razor.bindview.comthegnome@razor.bindview.com  References: –David Dittrich’s web site http://staff.washington.edu/dittrich/http://staff.washington.edu/dittrich/ –"Network Cat and Mouse", SANS Network Security '99, New Orleans; security presentation, http://www.sans.org http://www.sans.org –"The Paranoid Network", SANS 2000, Orlando; security presentation, http://www.sans.orghttp://www.sans.org –NMap, http://www.insecure.org/nmap/http://www.insecure.org/nmap/ –Icmpenum, http://razor.bindview.com/tools/http://razor.bindview.com/tools/ –Martin Roesch’s web site http://www.clark.net/~roesch/security.htmlhttp://www.clark.net/~roesch/security.html –“Strategies for Defeating Distributed Attacks”, http://razor.bindview.com/publish/papers/strategies.html http://razor.bindview.com/publish/papers/strategies.html –“Distributed Denial of Service Defense Tactics”, http://razor.bindview.com/publish/papers/DDSA_Defense.html http://razor.bindview.com/publish/papers/DDSA_Defense.html –Ofin Arkin, “ICMP Usage in Scanning”, http://www.sys- security.com/archive/papers/ICMP_Scanning_v2.01.pdfhttp://www.sys- security.com/archive/papers/ICMP_Scanning_v2.01.pdf