Presented by Nadine Sundquist

“On Scalable Attack Detection in the Network”

Ramana Rao Kompella, Sumeet Singh, and George Varghese

Presented by Nadine Sundquist

2 November 7, 2007 CS-622

Roadmap• Why do we need scalable attack

detection?• What are the difficulties in implementing

scalable attack detection?• What kinds of attacks can be detected?• What are Partial Completion Filters (PCFs)?• How do we use Partial Completion Filters?• What are the experimental results?






Why do w need scalable attack detection?

• Scalable: Able to detect network behavior at multi-gigabit speeds (at least 1 Gb/s).

• Detect behavior over a set of packets at network vantage points such as routers.

• Proposed solution: Aggregation (combining multiple connections) for attack detection?


Why Use Aggregation?

• Combining several lines into one is more efficient for forwarding.

• Can have millions of flows/connections with no enough high speed memory (on-chip and off-chip SRAM or cache) at router.

• Other services use forms of aggregation for faster processing. – Example: Internet lookup routers store 150

000 prefixes for the entire Internet to process requests faster.






Problems of AggregationBehavioral Aliasing: Good behaviors aggregateto look like bad behaviors.

False positive: Server thinks a resource is under attack,when traffic is in a normal state.

192.168.1.1

192.168.1.1

192.168.1.1

192.168.1.1

128.1.1.7

128.1.1.7128.1.1.7

128.1.1.7

2 computers look like 1 computer due to aggregation.


SYN 128.1.1.7:80SYN 128.1.1.7:80

Problems of AggregationSpoofing – Attacker avoids detection by appearing benign.

Our focus is TCP (Transport Control Protocol) SYN flooding, also known as Partial Completion Attacks: ConnectionsOpened, but not closed.

SYN – Connection request and connection opened.FIN – Connection finished/closed.

SYN 128.1.1.7:80SYN 128.1.1.7:80SYN 128.1.1.7:80FIN 128.1.1.7:80FIN 128.1.1.7:80

Attacker Victim

Firewall/Proxy/Victim Server(Does detection of SYN flooding)





10 November 7, 2007 CS-622

Kinds of Attacks

• Partial Completion Attacks• Attacks That Do Scanning• Bandwidth Attacks• Commonality = Bandwidth Tied Up

or Resources Tied Up

11 November 7, 2007 CS-622




12 November 7, 2007 CS-622

Partial Completion Filters (PCFs)

• New data structure.• Can detect scanning attacks and partial

completion attacks with small traffic volume.

• Can detect victims reacting to an attack.

• Only useful for TCP.• Only have a local geographical scope.

13 November 7, 2007 CS-622

Partial Completion Filters (PCFs)

SYN 192.168.1.1:20

FIN 192.168.1.1:20

SYN 10.1.1.5:24

SYN 10.1.1.5:24

SYN 10.1.1.5:24

Courtesy of Minsoo Choi, University of Southern California

If N packets delivered, stay within √N standard deviation.

If noise, 3 √N standard deviation.

5000 hash functions in experiments.(Requires 480 Kbits memory)

14 November 7, 2007 CS-622




15 November 7, 2007 CS-622

How do we use PCFs?

• Partial Completion Attacks

• TCP Scanning Detection

PCF(SYN, FIN, <Destination IP: Destination Port>)

PCF(SYN, FIN, <Source IP>)

16 November 7, 2007 CS-622

Where do I deploy PCFs?• Near sources -> Look at Source IP.

– Recognizes Scanning– Recognizes too many SYN packets w/o

FINs.

• Incoming/Outgoing edge of network -> Look at Destination IP. – Recognizes Attack

• Outgoing edge of network -> Look at Source IP. – Recognizes false FIN w/o FIN-ACK

17 November 7, 2007 CS-622




18 November 7, 2007 CS-622

Experiment Setup

ISP A ISP B

2 real flows of traffic from 1 dayOC-48 -> 2488.32 Mbits/second

Dir = DirectionISP = Internet Service Provider

Internet

Dir 0

Dir 0Dir 1

Dir 1

19 November 7, 2007 CS-622

How do we take into account bias?

-150 150SYN FIN Difference in Experiment

20 November 7, 2007 CS-622

Results• 5 million destinations (About 30 million

ports) & 2 million sources (About 30 million ports).

• 517 Attack Flows.• 6 False Positives -> Too many SYNs.• 0 False Negatives -> Too many FINs.• Could measure the time length of the

attacks.

21 November 7, 2007 CS-622

Scanning Detection• SYNs without FINs could mean port scans

A source doing port scanning will send SYN packets, but no FIN packets to MANY destinations (in red).

22 November 7, 2007 CS-622

Conclusions

• Speed requirement: Using aggregation is possible for attack detection on networks of at least 2488.32 Mbits/second.

• Memory requirement: Only uses 480 Kbits memory for hash functions.

• Accurate in a Local Area Network.

23 November 7, 2007 CS-622

Further Research/Work

• Run more tests using more sets of data. Only one set of data used in paper’s experiment.

• Research other methods of attack detection at high speeds and compare results.

• Further research scan-based (worm) attacks.

24 November 7, 2007 CS-622

References

• Ramana Rao Kompella, Sumeet Singh, and George Varghese, “On Scalable Attack Detection in the Network”, February 2007.

• Choi, Minsoo, “On Scalable Attack Detection in the Network Presentation”, netweb.usc.edu/ftp/pub/cs558f05/Slides/minsoo.ppt, 2007.

Documents

Presented by Nadine Sundquist