数据包过滤（packet filtering）是一个用软件或硬件设备对向网络上传或从网络下载的数据流进行有选择的控制过程。数据包过滤器通常是在将数据包从一个网站向另一个网络传送的过程中允许或阻止它们的通过(更为常见的是在从英特网向内部网络传输数据时，或从内部网络向英特网传输)。数据包过滤类防火墙对所有通过它进出的数据包进行检查，并阻止那些不符合既定规则数据包的传输。-Packet filtering (packet filtering) is a software or hardware device to the network upload or download data from the network flow selective control process. Packet filter is usually in packets from one network to another website of course they allow or prevent the passage of (more common in the internal network from the Internet to transmit data, or from the internal network to the Internet transmission). Type of packet filtering firewall through which all incoming and outgoing packet inspection, and to prevent those who do not comply with established rules of the transmission packet.