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Intrusion Detection Presentation : 2 OF n

Intrusion Detection Presentation : 2 OF n. by Manish Mehta 02/07/03. What will we discuss?. Network-Based Detection Network-based Architecture - Traditional Sensor-based - Distributed Network-node Network Intrusion Detection Engine - Signatures

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Intrusion Detection Presentation : 2 OF n

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  1. Intrusion DetectionPresentation : 2 OF n by Manish Mehta 02/07/03

  2. What will we discuss? • Network-Based Detection • Network-based Architecture - Traditional Sensor-based - Distributed Network-node • Network Intrusion Detection Engine - Signatures • Operational Concepts for network-based detection • Benefits of network-based ID • Challenges for network-based Technologies

  3. Introduction • Why you call it ‘network-based’? - used to analyze network packets. - packets are ‘sniffed’ off the network. • TCP/IP is the most common protocol targeted by commercial IDS. • Different technologies can resolve different levels of protocols through the application layer.

  4. Network-based Detection • Most network-based attacks are directed at OS vulnerabilities. • These can be exploited mainly towards following means • Unauthorized Access • Data/Resource Theft • Denial of Service

  5. Unauthorized Access Unauthorized Login - Key is to detect before/while logging in. - TFTP is well-known for lack of security. - SunOS 4.1.x had security problems with file sharing protocol. Jump-off Point - They are ‘bad’ and not ‘stupid’. - A compromised computer can open up several other computers in the same organization. - Why is my mail server contacting DoD?

  6. Data/Resource Theft Information theft - Password file download gives attacker the ability to compromise other systems. (look for ‘/etc/passwd’) - Secret Data file download Credit card numbers, Employee HR data Bandwidth Theft - Firms with lot of bandwidth not used at all times. - If the business of the attacker grows, he will be caught.

  7. Denial of Service Malformed Packets - Not all error conditions are taken care of while coding the protocol stack. - Code is not prepared to handle impossible situations in argument fields. Packet Flooding - Not a very sophisticated attack. - If source address is spoofed, it can be hard to deal with. Distributed DoS -Special case of Flooding (several machines attack at once) - ID is not a very good tool against this attack, but it can be helpful

  8. NID Architecture • Two types of NID Traditional Sensor-based (Promiscuous mode) - obtain packets, search for patterns, report alarms to the central command console. Network-node (Distributed) - Agent on each computer (for individual target)

  9. Traditional Sensor-based Architecture • Ethernet Chip in Promiscuous mode • “sniffed” packets are fed to the detection engine (typically on the same machine) • Taps are distributed to all mission-critical segments (generally one per segment) • Central command console correlates alarms from multiple sensors.

  10. Life cycle of a Packet • Packet is born. • “sniffed” off the wire in real-time by the sensor. (a stand-alone machine or a network device in promiscuous mode) • Detection engine matches the predefined patterns. If matched, Alert is generated and forwarded to central console. • Security officer is notified.

  11. Life cycle of a Packet (Contd.) • Response is generated. - Reconfiguring of routers/firewall rules - Terminate session • Alert is stored for later review and correlation. • Reports are generated. • Data forensics for long-term trends.

  12. Distributed Network-node Architecture • Sensor on every computer. • Every sensor is concerned about the target it resides on. • Now confused between host and network based?? - the difference between host and network based ID is the source of data • Network-node agents communicate with each other on the network to correlate alarms at the console.

  13. Life cycle of a Packet • Packet is born. • The packet is read in real-time through a sensor resident on the destination machine. • A Detection Engine is used to match signatures of misuse. If a pattern is found, an alarm is generated and forwarded to central console or other sensors on the network.

  14. Life cycle of a Packet (Contd.) • Security officer is notified. • Response is generated. - Reconfiguring of routers/firewall rules - Terminate session • Alert is stored for later review and correlation. • Reports are generated. • Data forensics for long-term trends.

  15. Misconception  Real-Time ID “I need Intrusion Detection” “Are you interested in network-based or host based?” “Oh, I need real-time Intrusion Detection” “Great, on the host or the network” “What???”

  16. Network Intrusion Detection Engine • This is where the real magic is !! • A stream of time sequential TCP/IP packets is processed to detect predetermined sequences and patterns (signatures). • Speed – An Issue.

  17. Network Signatures • Packet Content Signatures- based on contents of packets (smart ??) • Traffic Analysis Signatures- based on Header information and flow of traffic • More on detection mechanisms in future talks.

  18. Packet Content Signatures • Simple Example- Copy password file over FTP. - Look for pattern “passwd” in the packet. (Output of Snoop) Source.com  dest.com ETHER Type=0800(IP), size = 67 bytes IP D= 134.193.22.26 S=134.193.18.3 LEN=53, ID=34704 TCP D=21 S=2095 Ack=21233432 Seq=21342876 Len=13 Win=4096 FTP C port=2095 RETR \etc\passwd\r\n

  19. Traffic Analysis Signature • Simple Examples- A lot of packets destined to one machine in relatively short period of time.(An attempt of DoS attack) - A packet coming from outside the network with Source IP address as that of the inside network.

  20. Operational Concept • A NIDS only performs as well as it is operated. (configured) • The value of the system depends on the skills of the operator. • Network based ID may be used in a manner that requires very few resources.

  21. How do I use NIDSs? • The specific use of a NIDS is dependent on the environment-specific requirement. • Sensor placement plays an important role. Example: Sensor placed outside the firewall will identify source addresses attempting to attack you. Sensors placed inside the firewall will detect attacks that successfully circumvent your firewall. (IF you don’t have a Firewall, YOU SHOULDN’T BE HERE ! GO INSTALL IT FIRST !!)

  22. Operational Modes • Operational mode describes the manner in which you will operate your NIDS and partially describe the end goals of monitoring. • Two primary operational modes: - Tip-Off - Surveillance

  23. Tip-Off and Surveillance • The defining characteristic for tip-off The system is detecting something previously unsuspected. • Unlike tip-off, Surveillance takes place when misuse is already indicated or suspected. It is an increased effort to observe the behavior of a small set of objects.

  24. Benefits of NID • Outside Deterrence- A notification to the hacker can enhance the deterrent value of an IDS. • Threat Detection - Can be used deterministically or in a Decision Support Context. • Automated Response and Notification.- Pager, SNMP trap, On Screen, Audible, E-mail.

  25. Challenges for Network-based Technologies (promiscuous-mode) • Packet Reassembly (IP fragmentation)- can only search for patterns after reassembly. • High-speed networks (Gig E?) • Sniffer Detection Programs (Antisniff) • Switched Networks (IP over ATM?) • Encryption (IPSec, VPN)

  26. Questions ?

  27. Until then ..

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