Refused service attack protection method, network system and proxy server

The invention discloses a refusing service attacks protection method, a network system and a proxy server. Through intercepting a connection request packet, the invention obtains the source address of the connection request packet through the analysis and queries the legality of the matching connection request packet. To the connection request packet which cannot determine the legality, an agent objective end responses to the requests of clients, filters out the refusing service attacks and judges the address of the objective end according to the legal connection request response packet. The connection between the agent objective end and the objective end is constructed to realize the refusing service attacks protection. The invention can finish the integrated protection of local and remote servers.