Detector SherLOCK: Enhancing TRW with Bloom filters under memory and performance constraints

  • Authors:
  • Seung Yeob Nam;Hyu-Dae Kim;Hyong S. Kim

  • Affiliations:
  • Department of Information and Communication Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea;KAIST Institute for Information Technology Convergence, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea;Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States

  • Venue:
  • Computer Networks: The International Journal of Computer and Telecommunications Networking
  • Year:
  • 2008

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Abstract

Computer worms and bots are significant threats to large networks because they can spread very rapidly and are used for DDoS. The first phase of worms and bots begins by scanning vulnerable hosts. Missing on-going scanning activity can significantly deteriorate network performance. We propose a new scanning detection scheme, SherLOCK, based on the connection attempt success ratio. The proposed scheme can detect scanners with guaranteed false positive and false negative probabilities and with a limited memory size. Detection of scanners at high-speed links requires a high-speed memory and such memory devices are expensive and limited in size. We reduce the memory requirement by applying the Bloom filter. We show how slow scanners can be detected with a guaranteed performance for a given offered traffic load and memory size. This study can help to design the system that satisfies the target performance requirement. The detection performance is guaranteed under the assumption that malicious scanners and benign hosts have distinct behaviors in terms of the connection success ratio. We extend the proposed detector with a sampling mechanism to detect more intelligent scanners with guaranteed performance. These include scanners that use a list of pre-acquired IP addresses. We evaluate the performance of the proposed scheme through experiment using well-known traffic traces.