Disclosed is a method and apparatus for filtering received data packets. A hierarchical tree is maintained. The tree includes nodes organized in a plurality of levels. Each level above a root node of the tree has one or more of the nodes, with each of the one or more of the nodes corresponding to a particular value of a segment of an Internet Protocol (IP) address. The segment is the same for each node of a particular level of the tree. Each node at a particular level of the tree stores a number representative of the number of received packets having the same value for the segment of the IP address associated with the particular level. Some of the received data packets are filtered out based on the hierarchical tree.