Flow cleaning method, apparatus and system

The invention provides a flow cleaning method, apparatus and system. The method comprises the following steps: when abnormal flow is discovered, firstly modifying the DNS mapping of a terminal device, so that the IP address analyzed by the DNS for the domain name points to a flow cleaning center so as to transfer the flow that is originally sent to the terminal device to the flow cleaning center, and after the abnormal flow is cleaned, pointing the IP address with normal flow after the cleaning to the terminal device via address conversion so as to transmit the normal flow back to the terminal device. By adoption of the flow cleaning method, apparatus and system, the flow cleaning center can clean the devices beyond the metropolitan area network. When the terminal devices in other regions require flow cleaning, the flow cleaning center does not need to be deployed in the other regions again, and thus the application range of the flow cleaning center is wider. 本申请提供种流量清洗方法、装置和系统。本申请在发现异常流量时，先修改终端设备的DNS映射，使DNS针