Secondly, on the basis of introduction to the normal intrusion methods and state of art of network IDS, contemporary challenges and trends are discussed about IDS.

其次，在介绍常用入侵手段和网络入侵检测系统研究现状的基础上，讨论了当前入侵检测技术面临的挑战和发展趋势展望。

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Because the original deployments of IDS were just passive data collectors there was no impact on network performance from adding new signatures so the data base grew and grew and the logs IDS generated grew and grew to the point where even a mid-size organization would receive millions of alerts a day.

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