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The open source network intrusion detection system.

Snort. The open source network intrusion detection system. Secure System Administration & Certification Ravindra Pendyala. The main distribution site for Snort is http://www.snort.org. SNORT. IDS & History of Snort What is Snort? Features of Snort Snort Modes

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The open source network intrusion detection system.

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  1. Snort The open source network intrusion detection system. Secure System Administration & Certification Ravindra Pendyala

  2. The main distribution site for Snort is http://www.snort.org SNORT • IDS & History of Snort • What is Snort? • Features of Snort • Snort Modes • Compiling & Installing Snort • Snort Rules • Snort in different Modes • Using Snort • Third Party Enhancements • Conclusion

  3. NIDS & History of Snort Intrusion: An intrusion is somebody (A.K.A. "hacker" or "cracker") attempting to break into or misuse your system. NIDS: network intrusion detection systems (NIDS) monitors packets on the network wire and attempts to discover if a hacker/cracker is attempting to break into a system (or cause a denial of service attack).

  4. Martin Roesch is the founder and CTO of Sourcefire, Inc. NIDS & History of Snort... Snort was a true case of a programmer scratching his own itch. Here was Marty Roesch with his home network, wanting to see who, if anyone, was trying to penetrate it. This was a small and simple detection system for home use Initial Release on Dec 22 1998 - snort-0.96.tar.gz Latest Release on Oct 3 - snort-1.9.0.tar.gz

  5. Snort does NOT block intruders. Assumes a human is watching!!! What is Snort? Snort is a lightweight network intrusion detection system, capable of performing real-time traffic analysis and packet logging on IP networks. It can perform protocol analysis, content searching/matching and can be used to detect a variety of attacks and probes, such as buffer overflows, stealth port scans, CGI attacks, SMB probes, OS fingerprinting attempts, and much more. Snort uses a flexible rules language to describe traffic that it should collect or pass, as well as a detection engine that utilizes a modular plugin architecture. Snort has a real-time alerting capability as well, incorporating alerting mechanisms for syslog, a user specified file, a UNIX socket, or WinPopup messages to Windows clients using Samba's smbclient.

  6. Snort in simple words … • Automated tool to detect intrusions • Works locally (reactionary) or network wide (preemptive) • Preemptive IDS can use traffic monitoring or content monitoring • Does NOT block intruders. Assumes a human is watching!!!

  7. Operating Systems Snort works on following OS

  8. Features of Snort • “Lightweight” • Free • Portable • Runs on HP-UX, Linux, AIX, Irix, *BSD, Solaris, Win2K • Configurable with easy setup

  9. Snort Modes • Packet sniffer • Packet Logger • Preemptive IDS • - Actively monitors network traffic in real time to match intrusion signatures and send alerts

  10. Installing Snort • On Red Hat Linux 7.2, as root: • Download and install libpcap • Download and install these three .rpm: • libnet-1.0.2a-1snort.i386.rpm • snort-1.8.4-1snort.i386.rpm • snort-postgresql+flexresp-1.8.4-1snort.i386.rpm • Create /var/log/snort directory

  11. Installing Snort • Files installed: • /etc/snort contains conf and rule files • /var/log/snort will contain logs • /usr/sbin/snort contains snort binary • For a quick test, execute this command within the /etc/snort directory: snort –A console • From a separate machine, use nmap to generate events for Snort to detect: nmap –sP <snort_machine_IP_address>

  12. Installing on Windows 2000 • Download and install winpcap • Download & execute Snort184Win32.exe, select “typical” installation • mkdir “c:\Program Files\Sourcefire\Snort\log” • Files installed in c:\Program Files • Files\Sourcefire\Snort: • snort.conf • \rules directory contains rules • Snort.exe executable

  13. InstallingSnort • To test, execute this command within the c:\Program Files\Sourcefire\Snort directory: • snort –A console • From a separate machine, use nmap to generate events for Snort to detect: • nmap –sP <snort_machine_IP_address> • You should see an alert like this: • 03/27-15:18:06.911226 [**] [1:469:1] ICMP PING NMAP [**] • [Classification: Attempted Information Leak] [Priority: 2] • {ICMP} 129.244.70.17 -> 129.244.70.237

  14. Rules, Rules, Rules • Snort rules are extremely flexible and are easy to modify, unlike many commercial NIDS • Sample rule • alert udp $EXTERNAL_NET 53 -> $HOME_NET :1024 (msg:"MISC source port 53 to <1024";) • Rule alerts that anything from the external network coming in from port 53 and going to port 1024 should be flagged

  15. And More Rules • Elements before parentheses comprise ‘rule header’ • Elements in parentheses are ‘rule options’ • Rules can: Alert, Log, or Pass • Used for IP, UDP, ICMP • Source address / port • Destination address / port • Additional options • - This is where content matching can take place

  16. And More Rules • bad-traffic.rules exploit.rules scan.rules • finger.rules ftp.rules telnet.rules • smtp.rules rpc.rules rservices.rules • dos.rules ddos.rules dns.rules • tftp.rules web-cgi.rules web-coldfusion.rules • web-frontpage.rules web-iis.rules web-misc.rules • web-attacks.rules sql.rules x11.rules • icmp.rules netbios.rules misc.rules • backdoor.rules shellcode.rules policy.rules • porn.rules info.rules icmp-info.rules • virus.rules local.rules attack-responses.rules

  17. Good News Luckily you probably won’t have to write rules!

  18. Snort Modes • Sniffer: snort –dvae will be display payloads, be verbose, display arp traffic, and display link layer data • Packet Logger: snort –b –l /var/log/snort will log binary data to the /var/log/snort directory • NIDS: snort –b –l /var/log/snort –A full –c /etc/snort/snort.conf will log binary data in the /var/log/snort directory, with full alerts in /var/log/snort/alert, reading the configuration file in /etc/snort

  19. Third Party Enhancements • SnortSnarf www.silicondefense.com/software/snortsnarf/ • SnortSnarf is a Perl program to take files of alerts from the Snort to produce HTML reports • Output intended for diagnostic inspection • Silicon Defense also supplies sensors with commercial support • Description and screenshot taken from SnortSnarf web

  20. Third Party Enhancements • Analysis Console for Intrusion Databases (ACID) • acidlab.sourceforge.net/ • PHP-based analysis engine to search and process a database of security events generated by various IDSes, firewalls, and network monitoring tools • Query-builder and search interface, packet viewer (decoder), alert management, chart and statistics generation. • Description and screenshots taken from ACID web

  21. Conclusions • Snort is a powerful tool, but maximizing its usefulness requires a trained operator • Snort is considered a superior NIDS when compared to most commercial systems • Snort is a wonderful low to no cost solution for businesses. • Snort, written in C, can compile and run on variety of different Operating Systems.

  22. Online Resources Snort.org Securityfocus.com Whitehats.com

  23. Questions?

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