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Using Multiple Gateways to Foil DDOS Attack

Using Multiple Gateways to Foil DDOS Attack. by David Wilkinson. DDOS - Distributed Denial of Service. DDOS attack - host is flooded with packets that consume network bandwidth. Site becomes unavailable to legitimate users. February 2000: DDOS attacks shut down Yahoo, Ebay, Amazon.com, et al.

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Using Multiple Gateways to Foil DDOS Attack

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  1. Using Multiple Gateways to Foil DDOS Attack by David Wilkinson

  2. DDOS - Distributed Denial of Service • DDOS attack - host is flooded with packets that consume network bandwidth. Site becomes unavailable to legitimate users. • February 2000: DDOS attacks shut down Yahoo, Ebay, Amazon.com, et al. • October 2002: 13 root DNS servers attacked (not successful)

  3. Intrusion and attack phases Client (Intruder) ... Handler Handler Handler Systems Compromised ... ... ... A A A A A A Messages to broadcast addresses ... Replies to Victim Victim A = Agent

  4. Detail of attack net-a.com net-b.com net-c.com ... ... ... ... A A A A A A A A reflecting networks DNS DNS R DNS R reflecting networks R R R R R R R A = Agent R = Router Victim

  5. Solution: reroute traffic through multiple gateways • Idea: expand capability of DNS software, BIND, to handle ‘reroute’ command (opcode = 3) • reroute is sent to the authority DNS name server for each IP address in victim database; DNS message contains {victim host name, victim IP address, proxy server IP address} • named in each DNS server stores threetuple • resolver gets IP addresses of victim & proxy server from named and returns them to requesting application (ftp, telnet, http, etc.) • application stores IP address of victim in IP header (‘options’ field), and sends message to proxy server • proxy server forwards message to victim

  6. Traffic rerouted; attack foiled net-a.com net-b.com net-c.com ... ... ... ... A A A A A A A A reflecting networks DNS DNS R DNS R reflecting networks proxy proxy R proxy proxy R blocked by IDS blocked by IDS R blocked R R R blocked blocked A = Agent R = Router Victim reroute “Help!”

  7. Results thus far • Installed BIND9 on experimental machine, set up as primary DNS name server • client.c dispatches DNS message based on opcode. Added new branch for opcode = 3. • Compiled in new file, reroute.c, in the named directory to handle reroute msgs (not imp.) • Compiled in new file, detour.c, in the dig directory that will send the reroute command (not implemented) • Still three days left to accomplish something more impressive

  8. References • DNS and BIND. Paul Albitz and Cricket Liu, O’Reilly, 2001. • TCP/IP Illustrated, Volume 1: The Protocols. W. Richard Stevens, Addison Wesley, 1994. • Counter Hack. Ed Skoudis, Prentice-Hall, Inc., 2002. • “The ‘stacheldraht’ distributed denial of service attack tool.” David Dittrich, Univ. of Wash., Dec. 31, 1999. • “DRDoS: Distributed Reflection Denial of Service.” Steve Gibson, grc.com, Feb. 22, 2002. • “Consensus Roadmap for Defeating Distributed Denial of Service Attacks.” SANS Institute, sans.org, Feb. 23, 2000. • “Attacks Exposed Internet’s Vulnerabilities.” Brian Krebs and David McGuire, washingtonpost.com, Oct. 31, 2002.

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