A Testbed for Quantitative and Metrics Based Assessment of IDS

1. A Testbed for Quantitative and Metrics Based Assessment of IDS • By • Farhan Mirza 60-520

2. Contents • Introduction • Intrusion Detection System • Air Force Evaluation Environment • LARIAT • TIDeS • Tests and Results • Conclusion

3. Core Papers • Gautam Singaraju, Lawrence Teo, Yuliang Zheng, “A Testbed for Quantitative Assessment of IDS using Fuzzy Logic”, Laboratory of Information Integration Security and Privacy (LIISP), University of North Carolina at Charlotte Calpytix Security Corporation, USA, Appears in Proceeding of the Second IEEE International Information Assurance Workshop (IWIA ‘04) • P. Mell, V. Hu, R. Lippmann. J. Haines, and M. Zissman. “An overview of issues in testing intrusion detection systems”. NIST Interagency Report NIST IR 7007, NIST, http://csrc.nist.gov/publications/nistir/nistir-7007.pdf, June 2003 • E. Biermann, E. Clote, and L. Venter; “A comparison of Intrusion Detection Systems”; Computers and Security, Pages 676-683, 2001 • R. Lippman, J. W. Haines, D. J. Fried, J. Korba, and K. Das; “The 1999 DARPA Off-line Intrusion Detection Evaluation”; http://www.ll.mit.edu/IST/ideval/pubs/2000/1999EvalComputerNeworks2000.pdf • L. M. Rossey., R. K. Cunnigham, D. J. Fried, Jl C. Rabek, R. P. Lippmann, and J. W. Haines. Lariat: Lincoln adaptable real-time information assurance testbed. Fourth International Workshop on Recent Advances in Intrusion Detection, 2001 • T. G. Champion and R. S. Durst. Air force intrusion detection system evaluation environment. RAID Symposium, 1999

4. Introduction • Intrusion Detection System • Major investment for a firm • Common component in the corporate and home network • Growing in popularity • Commercial IDS are costly • Few are free, but effectiveness is doubtful

5. Introduction (Cont..) • IDSs employ different technologies • Claim to effectively detect an intrusion • In specific test environment - Technologies evokes question about their effectiveness and performance • Under scrutiny are network parameters – network bandwidth conditions, out-of-order packet sequence etc • Careful evaluations of IDSs are desired to check its effectiveness by varying network parameters [2]

6. IDS Testbeds • Testbed Development - Defense Advanced Research Projects Agency (DARPA) and Air Force in association with Lincoln Lab • Unavailable to public for evaluation • Air Force Evaluation Environment [7] • Lincoln Adaptable Real-Time Information Assurance Testbed (LARIAT) [3]

7. Metrics to quantify an IDS • Apart from strong testing scenario – required a robust and reliable metrics to quantify an IDS • One of the metrics suggested by National Institute of Standards and Technology (NIST) [4] • Based on quantitative analysis of IDS by varying network parameters • Legitimate and illegitimate traffic can easily be included for system testing • User should be able to customize the testbed • Other words - testbed should be built with plug-n-play architecture and be scalable

8. Air Force Evaluation Environment • Simulates the complexity of MAN found at military bases • Theoretically top-level firewall protect single entry point into base MAN • Size and diversity is simulated using software to dynamically assign arbitrary source protocol addresses • Uses two traffic generators • Outside machine – ran network sessions between the model base and simulated Internet • Inside machine – ran network sessions within the model base’s address space and simulated in presence of larger network • Entire testbed was completely isolated in AFRL’s laboratory

9. AFRL Virtual Test Network Architecture

10. AFRL Actual Physical Network

11. AFRL Traffic Generator Architecture • Five layers to design • The scheduler • The master controller • The slave layer • The automata layer • The virtual networking layer

12. Full-Time traffic generation system architecture

13. LARIAT – Lincoln Adaptable Real-Time Information Assurance Testbed • An extension of testbed created for DARPA 1998 & 1999 intrusion detection evaluations • Two design goals • Supports real-time evaluations • Create a deployable, configurable and easy-to-use testbed • Supports automated and quantitative evaluations • Components – generate realistic background user traffic and real network attacks, verify attack success or failure, score ID system performance • Provides graphical user interface to control and monitoring • Currently being exercised at four sites

14. LARIAT Experiment Steps • Initialize Network • Distribute Configuration • Pre-Conditions • Run Traffic • Verify and Score • Clean Up

15. Automated Run Sequence

16. LARIAT GUI

17. Software Components

18. Sample Attack Scenario available with LARIAT

19. Testbed for evaluating Intrusion Detection Systems (TIDeS) • Scalable architecture with rigid matrices for evaluation, that forms the foundation for the TIDeS framework • Evaluates IDSs on a common Platform • Based on Fuzzy Logic • User can customize the testing scenarios by being able to add or remove attacks from attack database • Allows a set of IDSs to determine the best IDS amongst them in specific environment

20. Testbed Architecture

21. Capabilities of TIDeS • To add new protocols • To add new scripts • Default protocols – HTTP, SMTP, POP3, TELNET, FTP and SSH • Depend on scenario - Data is captured from short time to 24/7

22. Testing Scenarios • Non-environmental based testing scenario • Does not depend on data that has been collected on the network • Test Conducted in this Scenario • All-legitimate traffic testing • Launches only legitimate traffic • Network traffic is increased till network breaks down • # of false alarms determined and classified as false positives • All-illegitimate traffic testing • Launches only attacks from attack database • Network traffic is increased till network breaks down • If attack is not detected by IDS, it could be classified as false negative • Mixed traffic testing • Launches both legitimate and illegitimate traffic • Traffic generated randomly and launched traffic is logged • Network traffic is increased till network breaks down • IDS output and logged launch traffic profile determine false alarms

23. Testing Scenarios(Cont…) • Environmental based testing scenario • Depends upon the traffic that has been captured from the user’s network • Important as the IDS evaluation performed under the actual network condition • Such a testing of entire spectrum of conditions leads to the effective evaluation of IDSs • The results from testing is provided to Fuzzy Logic evaluation Framework

24. Components of TIDeS Architecture • Handler • Virtual Machine Emulator • Launcher • Environment Profile Generator • Scripts • Evaluation Framework

25. Handler • Main Controller • An Interface to the testbed • Provides capability of monitoring the tests

26. Virtual Machine Emulator • Emulates numerous virtual machines with unique IP addresses • Maps entire network into a single computer • Capability to emulate routers and each virtual machine can have a different OS • Virtual network setup is created • Honeyd is used

27. Launcher • Launcher generates traffic when a control signal is received from handler through the agent and then to virtual machine emulator • Launcher in turn activates the scripts that generate traffic • Launcher then launch environment profile • Handler activates the launcher • Accessing the different services – the scripts create the traffic on the network

28. Environment Profile Generator • Used to generate the environmental traffic patterns of the user’s network • Generated from the real-time condition by analyzing networks • Environment profile is exported to the machine that hosts the virtual machine emulator • Traffic generator generates different environment profiles for each of the IP address

29. Environment Profiles in TIDeS framework • University Environment Profile • Stand-alone Environment Profile • Home Environment Profile

30. University Environment Profile • Number of Server used – 4 • All servers used in University environment • Server 1 – Accepts HTTP connections • Server 2 – Interactive server that accepts SSH, TELNET and FTP connections • Server 3 – One of 2 mail servers, accepts SMTP connections • Server 4 – Other mail server, accepts POP and IMAP connections • Both mail servers also accept SSH connections only for management staff • Servers run on Sun Solaris OS • Snoop is used as packet capturing application developed by Sun Microsystems • Servers are working for working day period of a day

31. Home Environment Profile • Generated by monitoring a Home system • Exposed to many attacks from the Internet for short duration • Typically connect using modems, over slow connection usually at 56kbps • Profile need not be monitored for longer period and hence have different evaluation scenario • Connections and data throughput is measured for 3-hours period

32. Stand-alone Environment Profile • Generated to monitor a Stand-alone system • Connected to the system and is not disconnected from the system for long periods of time • Connected to broadband • Vulnerable to attacks from Internet and also from insider attacks • Monitored for 24 hours a day for 7 days a week

33. Scripts • Operating system independent and activated by launcher • Connect the server and interact with there service on the server • 6 legitimate scripts and 40 attack scripts used in TIDeS

34. Few of Default Attack Scripts with TIDeS

35. Evaluation Framework • TIDeS - many parameters for IDS evaluation • Depth – defined as number of attacks detected by the system to the total number of known attacks • Breadth – defined as the number of unknown attacks to the attacks detected that fall outside the framework of system’s attack database • False alarms – performance under stress, reliability and accuracy of detecting individual attacks • Evaluation - based on error rate and network load parameters • Decision making process – Based on fuzzy logic and fuzzy rules • Performance evaluation are performed using false positives, false negatives, and cumulative false alarms

36. Evaluation Metrics • Managerial and architectural Metrics • Performance Metrics • Analytical Metrics • Interactivity Metrics

37. Managerial and Architectural Metrics • Evaluate the architecture efficiency of an IDS • Matrics are: • Distributed Management • Determines the distribution capabilities among different analyzers • Configuration Difficulty • How well a user understands the deployment of an IDS would enable a correct deployment of the IDS • Ease of Policy and License Management • Ease of setting security and intrusion detection policies as well as the difficulty in obtaining, updating and extending licenses • Availability of Updates • Availability and cost of updates of signature and/or behavior profiles as well as the availability and cost of product upgrades

38. Managerial and Architectural Metrics (Cont…) • Adjustable Sensitivity • Ease of altering the sensitivity of IDS at various times and for different environments in order to achieve a balance between false positive and false negative error rates • Data Storage Capacity Needs • Amount of disk space consumed for storing the signature profiles, logs and other application data. • Scalable Load Balancing • Measures the ability of an IDS to partition traffic into independent, balanced sensor loads, and the ability of load-balancing sub process to scale upwards and downwards

39. Performance Metrics • Measure and evaluate the parameters that impact the performance of the IDS • Metrics are: • Observed False Positive Ratio • This is the ratio of alarms wrongly raised by the IDS to the total number of transactions. The False Positive Ratio is given by • False Negative Ratio • This is the ratio of actual attacks that are not detected by the IDS to the total number of transactions. This is given by 1 2

40. Performance Metrics (Cont..) • Cumulative False Alarm Rate • The weighted average of False Positive and False Negative ratios • Induced Traffic Latency • Given by the delay measured in the arrival of the packets at the target network in the presence and absence of an IDS. • Stress Handling and Point of Breakdown • Point of breakdown of an IDS is defined as the level of network or host traffic that results in a shutdown or malfunction of IDS. It is measured as packets/sec or number of simultaneous TCP streams • IDS Throughput • Defined as the observed level of traffic up to which the IDS performs without dropping any packets.

41. Analytical Metrics • Depth and Breath of System’s Detection Capability • Depth: defined as the number of attack signature patterns and/or behavior models known to it. • Breadth: given by the number of attacks and intrusions recognized by the IDS that lie outside its knowledge domain • Reliability of Attack Detection • Defined as the ratio of false positives to total alarms raised. Reliability of attack detection is given by 3

42. Analytical Metrics (Cont..) • Possibility of Attack • Defined as the ratio of false negatives to true negatives. Possibility of attack is given by • Consistency • Given by the variation in the performance (false positive and false negative measurement) of an IDS under varying network load and traffic environments • Error Reporting and Recovery • Extent of event notification and logging. This is again a subjective criteria requiring user discretion 4

43. Interactivity Metrics • These are again a set of subjective metrics demanding user analysis • These metrics are: • Firewall Interaction: Ability to interact with the Firewall systems • Router Interaction: Degree to which an IDS interacts with the router and redirects attacker’s traffic to a Honeypot • SNMP interaction: Ability of an IDS to send an SNMP trap to one or more network devices in response to a detected attack • User friendliness: The ease to set up and configure an IDS in users’ environment

44. Fuzzy Logic Basics • Fuzzy Set • extension of classical set theory and are used in fuzzy logic • involve in capturing, representing and working with linguistic notations • objects with unclear boundaries • Fuzzy Systems • knowledge-based or rule-based systems at the heart of which is a knowledge-base system consisting of so-called fuzzy IF-THEN rules • A fuzzy IF-THEN rule is an IF-THEN statement • Example: Fuzzy IF-THEN rule: IF the false alarm rate of the IDS is high, THENlesserscoreisawardedtotheIDS

45. Fuzzy Logic with IDS • Fuzzy Logic – provides simple non-linear logical solution to the problem of measuring IDS capabilities • Fuzzy set approach – starts off by encapsulating all available domain knowledge and organizing it into a manageable format • Collection of IF-THEN rules forms a suitable control and decision making protocol • These rules include linguistic terms given in above equation

46. IDS testing and evaluation Basic Tests - Test 1: Testing for False Alarms • Case 1: False Positive • Only attack traffic launched • Network load is measured as % of total network bandwidth • % false positive alarms are measure as per equation 1 • Mapping the %FP and average network loads during the testing phase, onto their respective fuzzy sets • Testing is carried out until system breaks down

47. Test 1: Testing for False Alarms • Case 2: False Negative • Similar process is repeated for false negatives with only legitimate traffic launched the IDS • Amount of traffic predicted as attacks now become the false negatives • Similar calculations are made for false negatives giving us the output false negative performance set • Case 3: Cumulative False Alarms • Output sets obtained in the above tests are fed back to the fuzzy evaluator to obtain a cumulative performance report for the system. • This process is known as forward chaining, where the fuzzy result of one test is forwarded for further evaluation • The evaluation process would be similar to the above discussed method, giving us a precise grade for the system’s error rate performance on a fuzzy scale

48. Test 2: Consistency and Reliability • Error consistency test • The test is similar to test 1 • However, network traffic is a mixture of legitimate as well as attack traffic • The %error in this case is measured as follows: • The performance of the IDS tested at various network loads and its consistency checked against the results of test 1 • Besides error consistency, also measure the ratio of %FP to %FN. The possibility of attack given by Percentage possibility of Attack = 5 6

49. Results • Various quantitative analysis is performed on the IDS during the testing phase with the TIDeS framework • Evaluations performed on the working of well-known IDS • Preliminary results • Alerts generated by an IDS when there was no illegitimate traffic launched on the network • Testing launched 897 legitimate traffic transactions • Total 170 attacks were detected under a network load of 10% of a T1 LAN connection • Indicates an 18.5% error in the detection capabilities

50. Conclusion • Testing and Selecting an IDS is a major challenge • TIDeS Testbed – allows users to select best IDS for specific customized environment • Based on reliable and robust metrics • Development of traffic profiles and evaluation framework allows TIDeS to be built to evaluate systems in users environment • Fuzzy logic Evaluation Framework can also be used to evaluate an IDS