Abstract: The invention relates in particular to a method of protecting a server (10) against denial of service attacks wherein, when setting up a communication session between a client (26) and the server, the setting up of that session being requested by the client for the provision of a service: the server receives (52) a request to provide service sent by the client; the server sends (54) an agreement to provide service to the client; the server waits (56) for an acknowledgement of the agreement from the client within a time period determined beforehand by the server. During this exchange of data, intermediate equipment (30) intercepts the data exchanged between the client and the server. Furthermore, if a criterion determined beforehand by the intermediate equipment is satisfied during this exchange of data, the intermediate equipment interrupts the setting up of the session requested by the client.

Abstract: The invention relates to a method of protecting a server (10, 18) against denial of DNS service attacks wherein denial of DNS service attacks targeting the server are detected (100, 102, 104) and data packets addressed to the server are intercepted (110). The transmission of an intercepted data packet to the server is interrupted (116) if the intercepted packet has a transaction number that is not in a list of transaction numbers of requests sent by the server.