Network Intrusion Detection Systems

1. Network Intrusion Detection Systems Slides by: MM Clements A Adekunle The University of Greenwich

2. Intrusion Detection Detection and protection from attacks against networks Three types of network attacks • Reconnaissance • Access • Denial of service Engineering and Management of Secure Computer Networks

3. Intrusion detection system (IDS) • An Intrusion detection system (IDS) is software or hardware designed to monitor, analyze and respond to events occurring in a computer system or network for signs of possible incidents of violation in security policies. • These incidents of violations can be unwanted attempts to access, manipulate or disable computer systems, mainly via a network, such as the Internet. Engineering and Management of Secure Computer Networks

4. Classification of Intrusion Detection Profile or Anomaly based intrusion detection • Monitors network traffic and compares it against an established baseline for normal use • Bandwidth, protocols, ports and devices generally connecting to each other • Alerts the administrator or user when traffic is detected which is anomalous, or significantly different, than the baseline. • Example: Snort Spade plug-in • Prone to high number of false-positives Engineering and Management of Secure Computer Networks

5. Classification of Intrusion Detection Signature based intrusion detection • Also known as Misuse Detection • A signature based IDS will monitor packets on the network and compare them against a database of signatures or attributes from known malicious threats. • Similar to the way most antivirus software detects malware. • Examples: Cisco Sensors 4200 series, Snort • Less prone to false positives • Unable to detect zero-day threats whose signatures are not available Engineering and Management of Secure Computer Networks

6. Types of Intrusion Detection Systems Host based intrusion detection Systems • Software (Agents) installed on computers to monitor input and output packets from device • It performs log analysis, file integrity checking, policy monitoring, rootkit detection, real-time alerting and active response. • Examples: • Cisco Security Agent (CSA) , OSSEC, Tripwire Engineering and Management of Secure Computer Networks

7. Host-Based Intrusion Detection Corporate network Agent Agent Untrustednetwork Firewall Agent Agent Agent Agent Agent Agent WWW server DNS server Engineering and Management of Secure Computer Networks

8. Types of Intrusion Detection Systems Network-Based Intrusion Detection Systems • Connected to network segments to monitor, analyze and respond to network traffic. • A single IDS sensor can monitor many hosts • NIDS sensors are available in two formats • Appliance: It consists of specialized hardware sensor and its dedicated software. The hardware consists of specialized NIC’s, processors and hard disks to efficiently capture traffic and perform analysis. • Examples: Cisco IDS 4200 series, IBM Real Secure Network • Software: Sensor software installed on server and placed in network to monitor network traffic. • Examples: Snort, Bro, Untangle Engineering and Management of Secure Computer Networks

9. Network-Based Intrusion Detection Corporate network Sensor Sensor Firewall Untrustednetwork DNS server WWW server Management System Engineering and Management of Secure Computer Networks

10. Sensor Appliance Interfaces Untrusted Network Monitoring Interface Router Switch Sensor Router Protected Network Command and Control Interface Management System Engineering and Management of Secure Computer Networks

11. 1 2 3 Promiscuous-Mode Protection: IDS A network device sends copies of packets to the sensor for analysis. 2 If the traffic matches a signature, the signature fires. Switched Port Analyzer (SPAN) Switch The sensor can send an alarm to a management console and take a response action such as resetting the connection. Sensor Management System Target Engineering and Management of Secure Computer Networks

12. Inline-Mode Protection: IPS The sensor resides in the data forwarding path. Sensor An alert can be sent to the management console. If a packet triggers a signature, it can be dropped before it reaches its target. Management System Target Engineering and Management of Secure Computer Networks

13. IDS and IPS Deployment Considerations • Deploy an IDS sensor in areas where you cannot deploy an inline device or where you do not plan to use deny actions. • Deploy an IPS sensor in those areas where you need and plan to use deny actions. Engineering and Management of Secure Computer Networks

14. IDS and IPS Deployment Comparison Inside Attacker Internet Sensor on Outside: • Sees all traffic destined for your network • Has high probability of raising false alarms (false positives) • Does not detect internal attacks Sensor on Inside: • Sees only traffic permitted by firewall • Has lower probability of false alarms (false positives) • Requires immediate response to alarms Engineering and Management of Secure Computer Networks

15. Network based IDS and IPS Deployment Router Firewall Switch Switch IPS Sensor UntrustedNetwork IDS Sensor Switch Management Server Corporate Network WWW Server DNS Server DMZ Engineering and Management of Secure Computer Networks

16. IDS and IPS deployment example in an Enterprise Network Branch Corporate Network NM-CIDS Router Firewall UntrustedNetwork Sensor Sensor Management Server DMZ Agent Agent WWW Server DNS Server Engineering and Management of Secure Computer Networks

17. CiscoIDS Family 600 250 IDSM-2 IDS 4255 200 IPS 4240 Performance (Mbps) 80 AIP-SSM 45 IPS 4215 NM-CIDS 10/100/1000 TX 1000 SX 10/100/1000 TX Switched/1000 10/100/1000 TX 10/100 TX 10/100/1000 TX Network Media

18. Snort Open source, freely available software except for rules Installed as dedicated server on Windows and Linux, Solaris operating systems Placed as network sensor in a network Rules are set of instructions defined to take certain action after matching some sort of signatures (atomic or composite) • Example: • alert tcp $HOME_NET any -> $EXTERNAL_NET any (content:"uk.youtube.com”;msg:"someone visited YouTube";)‏ Engineering and Management of Secure Computer Networks

19. Snort Modes • Sniffer Mode • Used to sniff traffic from network • Traffic will be captured using libpcap or winpcap. • Traffic will be captured directly from the sensor . • Logger Mode • Simple logging into a file. Two possible formats are Binary and ASCII. • Logging into a Database (eg. MySQL)‏ • Can be used for creating the normal traffic profile • Intrusion Detection / Prevention • The rules will be used in this mode of snort to detect unwanted activity Engineering and Management of Secure Computer Networks

20. IDS/IPS Vulnerabilities • Cisco IPS Packet Handling DoS -  • In July 2006, a DoS vulnerability was discovered on Cisco IPS 4200 series models which were running version 5.1 software. • Snort Rule Matching Backtrack DoS - • Snort versions 1.8 through 2.6 had a DoS vulnerability , found on January 11, 2007 which can exploit Snort's rule matching algorithm by using a crafted packet. This could cause the algorithm to slow down to the point where detection may become unavailable. Snort was quick to release version 2.6.1 which corrected this issue. Engineering and Management of Secure Computer Networks

21. How to protect IDS? • Don't run any service on your IDS sensor. • The platform on which you are running IDS should be patched with the latest releases from your vendor. • Configure the IDS machine so that it does not respond to ping (ICMP Echo-type) packets. • User accounts should not be created except those that are absolutely necessary. Engineering and Management of Secure Computer Networks

22. Unified Threat Management (UTM) • Unified Threat Management (UTM) is a network device that have many features in one box, including: • IDS, IPS, Firewall, Spyware, Anti Spam , Anti Phishing • Anti Virus, Content (www) Filter, VPN • Example: Untangle, Watchguard • Untangle Demo: http://www.untangle.com/video_overview/ Engineering and Management of Secure Computer Networks

23. Summary Intrusion detection system (IDS) is software or hardware designed to monitor, analyze and respond to network traffic . • Can be classified as Profile or Signature based intrusion detection. • Signatures can be defined as Atomic or Composite. • Can be available as Host or Network based Intrusion detection . • IDS is used as promiscuous mode protection in DMZ • IPS is used as Inline mode protection for securing internal network • Cisco 4200 series IDS and IPS sensors offer rich set of features for ISD and IPS • Snort is an open source, free IDS and can operate in sniff , logging and Intrusion detection/prevention modes. Snort uses rules to analyze traffic. • IDS/IPS software can be vulnerable to exploits so run patched version, and shutdown unnecessary services. Unified Threat Management (UTM) is a network device that have many features in one box. E.g, Untangle, Watchguard. Engineering and Management of Secure Computer Networks