STRING SEARCHING ENGINE FOR VIRUS SCANNING Author ： Derek Pao, Xing Wang, Xiaoran Wang, Cong Cao, Yuesheng Zhu Publisher ： TRANSACTIONS ON COMPUTERS, 2012 Presenter ： Jia-Wei,You Date ： 2012/3/7 1

Introduction Intrusion detection system (IDS) and anti-virus software are essential security tools for today’s computer systems. Hence, the memory cost of pure AC-based methods cannot be lower than 8 bits per character. Updates to the pattern set in an anti-virus system can be quite frequent. However, if all virus signatures were to be stored in the on-chip embedded memory, it would require at least 20Mbyte-200Mbyte memory space. 2

Introduction Quick sampling plus verification (QSV) approach. In our approach of performing string matching over a very large virus signature set (82888 static strings), only 1.4Mbyte on chip memory is required, about 1.4 bits per character of the signature set. The QSV system can be updated by only updating the lookup tables, without reconfiguring the circuit. 3

QSV 4

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Aggregation Unit 10

pid, patLoc, refLoc, verified, which are the pattern ID, location of the last byte of the pattern found in the input stream, location of the last byte of the 16-byte prefix, flag indicating whether the pattern has been verified by a CRC unit respectively. 11

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Performance ClamAV virus database (main.cvd version 51 released on 14 May 2009) 13

Performance 14

Performance Using the Xilinx Virtex-5 XC5VSX240T device model Design uses 324 (63%) 36-Kbit block RAMs, 4878 (3.3%) LUTs, 6989 (4.7%) register bits and occupies 2163 (5.8%) slices. maximum system clock frequency is 200MHz 1.4 bits per character. 15