To　simplify　the　construction　of　an　intrusion　detection　system,　a　sensor　component　for　network-based　intrusion　detection　system　is　designed　and　implemented.　This　component　can　be　used　to　grasp　data　packet　from　network,　to　reconstruct　the　IP　packet,　to　reestablish　the　TCP　layer　data　flow　and　to　restore　data　of　application　layer.　Based　on　the　module　designing　method,　the　component　is　highly　reusable　and　expandable.　With　the　support　of　＂loading　according　to　configuration＂　mechanism,　users　can　readily　add　to　or　remove　a　module　from　this　component.　This　mechanism　enables　users　to　customize　the　component　on　the　demand　of　specified　requirements　so　as　to　make　the　system　more　efficient.