1 / 12

The Latest In Denial Of Service Attacks: “Smurfing”

The Latest In Denial Of Service Attacks: “Smurfing”. Description and Information to Minimize Effects Craig A. Huegen <chuegen@cisco.com> Cisco Systems, Inc. NANOG 11 Interprovider Operations BOF. 971027_smurf.ppt. Description of “Smurfing”. Newest DoS attack

brett-vincent
Download Presentation

The Latest In Denial Of Service Attacks: “Smurfing”

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Latest In Denial Of Service Attacks: “Smurfing” Description and Information to Minimize Effects Craig A. Huegen <chuegen@cisco.com> Cisco Systems, Inc. NANOG 11 Interprovider Operations BOF 971027_smurf.ppt

  2. Description of “Smurfing” • Newest DoS attack • Network-based, fills access pipes • Uses ICMP echo/reply packets with broadcast networks to multiply traffic • Requires the ability to send spoofed packets • Abuses “bounce-sites” to attack victims • Traffic multiplied by a factor of 50 to 200

  3. Description of Smurfing (cont’d)

  4. Multiplied Bandwidth • Perpetrator has T1 bandwidth available (typically a cracked account), and uses half of it (768 Kbps) to send spoofed packets, half to bounce site 1, half to bounce site 2 • Bounce site 1 has a switched co-location network of 80 hosts and T3 connection to net • Bounce site 2 has a switched co-location network of 100 hosts and T3 connection to net • (384 Kbps * 80 hosts) = 30 Mbps outbound traffic for bounce site 1 • (384 Kbps * 100 hosts) = 37.5 Mbps outbound traffic for bounce site 2 • Victim is pounded with 67.5 Mbps (!) from half a T1!

  5. Profiles of Participants • Typical Perpetrators • Cracked superuser account on well-connected enterprise network • Superuser account on university residence hall network (Ethernet) • Typical PPP dial-up account (for smaller targets) • Typical Bounce Sites • Large co-location subnets • Large switched enterprise subnets • Typically scanned for large numbers of responding hosts • Typical Victims • IRC Users, Operators, and Servers • Providers who eliminate troublesome users’ accounts

  6. Prevention Techniques • How to prevent your network from being the source of the attack: • Apply filters to each customer network • Ingress: • Allow only those packets with source addresses within the customer’s assigned netblocks • Apply filters to your upstreams • Egress: • Allow only those packets with source addresses within your netblocks to protect others • Ingress: • Deny those packets with source addresses within your netblocks to protect yourself • This also prevents other forms of attacks as well

  7. Prevention Techniques • How to prevent being a “bounce site”: • Turn off directed broadcasts to subnets with 5 hosts or more • Cisco: Interface command “no ip directed-broadcast” • Proteon: IP protocol configuration “disable directed-broadcast” • Bay Networks: Set a false static ARP address for bcast address • Use access control lists (if necessary) to prevent ICMP echo requests from entering your network • Probably not an elegant solution; makes troubleshooting difficult • Encourage vendors to turn off replies for ICMP echos to broadcast addresses • Host Requirements RFC-1122 Section 3.2.2.6 states “An ICMP Echo Request destined to an IP broadcast or IP multicast address MAY be silently discarded.” • Patches are available for free UNIX-ish operating systems.

  8. Prevention Techniques • If you do become a bounce site: • Trace the traffic streams to the edge of your network, and work with your upstream or peer in order to track the stream further • MCI’s DoSTracker tool • Manual tracing/logging tips

  9. Prevention Techniques • How to suppress an attack if you’re the victim: • Implement ACL’s at network edges to block ICMP echo responses to your high-visibility hosts, such as IRC servers • Again, will impair troubleshooting -- “ping” breaks • Will still allow your access pipes to fill • Work with upstream providers to determine the help they can provide to you • Blocking ICMP echoes for high-visibility hosts from coming through your access pipes • Tracing attacks

  10. Prevention Techniques • Technical help tips for Cisco routers: • BugID CSCdj35407 - “fast drop” ACL code • This bug fix optimizes the way that packets denied by an ACL are dropped within IOS, reducing CPU utilization for large amounts of denied traffic. • First major release of integration is 11.1(14)CA • Not available in 11.2 yet, but coming • BugID CSCdj35856 - ACL logging throttles • This bug fix places a throttle in IOS which will allow a user to specify the rate at which logging will take place of packets which match a condition in an ACL where “log” or “log-input” is specified. • First maintenance release of integration is 11.1(14.1)CA • Not available in 11.2 yet, but coming

  11. References • White paper on “smurf” attacks: • http://www.quadrunner.com/~chuegen/smurf.txt • Ingress filtering: • ftp://ds.internic.net/internet-drafts/draft-ferguson-ingress-filtering-03.txt • MCI’s DoSTracker tool: • http://www.security.mci.net/dostracker/ • Other DoS attacks: • “Defining Strategies to Protect Against TCP SYN Denial of Service Attacks” • http://www.cisco.com/warp/public/707/4.html • “Defining Strategies to Protect Against UDP Diagnostic Port Denial of Service Attacks” • http://www.cisco.com/warp/public/707/3.html

  12. Author • Craig Huegen • <chuegen@cisco.com> • -or- • <chuegen@quadrunner.com>

More Related