Exercise #2

Blackholes, Sinkholes, and Traceback

What you will get out of this exercise:

• learn to configure low-level networking on a modern OS, and on modern router OSs
• a hands-on understanding of how backbone routing in the Internet works today
• a hands-on experience with real-life ISP techniques to deal with DDoS attacks

• Configuring BGP in Cisco Routers
• The Zebra Routing Toolkit
• BGP configuration in Zebra
• packit

In addition, you will be asked to submit data files and other kinds of files. To do this, put your report and all required files into a directory named ex2. Then tar and gzip this directory into a file called ex2.tar.gz and submit it electronically. (Read the documentation for the Unix "tar" command on how to do this).

Even if you are not able to complete the exercise, be sure to submit a partial lab report. You will get partial credit for your efforts.

Setting up the interfaces

You will need to set up an address assignment plan for the topology. Setup the first two bytes of all addresses according to the last four digits of your USC ID. If your USC ID is abcdefghij, then all addresses must begin with 1gh.ij. For example, if your USC ID is xxxxxx1234, then all addresses must be in the form of 112.34.x.x.

Remote Blackholing

In this step, you will implement remote blackholing. First, you will setup the topology shown below and configure routing. Then, you will use packit to launch attacks from the three attackers toward the target machine. Finally, you will login to R2 and propagate a blackhole route, which should reach all the other routers and stop the attack on the target.

In this topology, R1, R2 and R3 are Cisco routers and the other machines are Unix workstations. A1, A2 and A3 are attackers running packit.

While the experiment is on going, you should also collect binary packet traces on the Target using tcpdump without filtering out any traffic. Read the man page for tcpdump carefully before embarking on the experiment.

Answer these questions in your lab report.

1. Write in your report the address configuration for all interfaces.
2. Run BGP on all routers and configure them in the same Autonomous System. Figure out how to implement remote blackholing at the routers. Learn about the Null0 interface, BGP static routes and the ip next-hop command. Include the running-config of routers R1, R2 and R3. Call these files r1.blackholing.conf, r2.blackholing.conf, etc.
3. Start a TCP SYN attack. Make sure the source addresses are randomized. What command options did you use?
4. Logon to R2 and issue the appropriate commands to blackhole the target. What commands did you use? What happens at the Target?
5. Logon to R1, R2, and R3 and issue ping commands to the Target. List the commands you use and the output. Explain what happens.
6. Compress the trace from the Target and include it in your submission. The trace must be named target.blackholing.trace.gz.

Sinkholing

For this step, you will implement a Sinkhole to divert attack packets to a sinkhole machine.

Configure the topology shown below.

The Sinkhole runs Zebra. As with Part 1, the attackers A1 and A2 will use packit and randomized source addresses.

While the experiment is on going, you should also collect binary packet traces on the Target and the Sinkhole using tcpdump without filtering out any traffic. Read the man page for tcpdump carefully before embarking on the experiment.

Answer these questions in your lab report.

1. Write in your report the address configuration for all interfaces.
2. Include the zebra bgpd files from the Sinkhole. Call the file sinkhole.sinkholing.bgpd.conf. Also include the running-config of routers R1, R2 and R3. Call these files r1.sinkholing.conf, r2.sinkholing.conf, etc.
3. Start an ICMP ECHO attack. What command options did you use?
4. Issue the appropriate zebra commands at the sinkhole machine to divert all attack traffic from the target to the sinkhole. What commands did you use?
5. Compress the traces from the Target and the Sinkhole. Include them in your submission. These traces must be named target.sinkholing.trace.gz and sinkhole.sinkholing.trace.gz.

Traceback

The final step in the exercise is to trace back the attack streams at the edge of your network. Remember that in real life, an ISP may have many links to other networks but only a subset of them will carry attack traffic for any given attack. In this part we will combine remote blackholing and sinkholing to implement a traceback technique that will reveal the ingress interfaces of the attack. The technique will use a sinkhole to attract a subset of the ICMP unreachable messages generated by routers after the target address is blackholed. For this technique to work you need to configure your sinkhole to advertise a large, unused IP address space. To find such a space go to the IANA web page and pick an appropriate IP range.

Configure the topology as the sinkholing experiment.

While the experiment is on going, you should also collect binary packet traces on the Target and the Sinkhole using tcpdump without filtering out any traffic. Read the man page for tcpdump carefully before embarking on the experiment.

Answer these questions in your lab report.

1. Write in your report the address configuration for all interfaces.
2. Include the zebra bgpd files from the Sinkhole. Call the file sinkhole.traceback.bgpd.conf. Also include the running-config of routers R1, R2 and R3. Call these files r1.traceback.conf, r2.traceback.conf, etc.
3. Execute a TCP SYN attack. Write the command line options you used in your report.
4. Figure out how to use a combination of blackholing and sinkholing, along with the unused address space you picked to divert ICMP unreachables to your sinkhole. Explain how you did this in your report.
5. Determine the IP address of the interfaces the attack is coming through. Write those in your report. How did you determine these addresses?
6. Compress the traces from the Target and the Sinkhole. Include them in your submission. These traces must be named target.traceback.trace.gz and sinkhole.traceback.trace.gz.

Discussion

Answer the following questions in your lab report.

• Why is Blackholing useful? (1-2 sentences)
• Why is Sinkholing useful? (1-2 sentences)
• Why is Traceback useful? (1-2 sentences)
• Based on your observations, how long would it take to discover the ingress points of a DDoS attack?
• How easy or difficult are these techniques to implement? Try to extrapolate on a large network with perhaps thousands of internal routers and dozens of border routers.
• Are these techniques sufficient to counter DDoS attacks? If no, explain.

You're done! Submit the report electronically as outlined above.