Method of gaining secure access from a host (13) to Intranet resources provided by at least a content server (18) in a data transmission system wherein the host is connected to the content server through a gateway (17). Such a method consists in generating and sending at predetermined transmission instants from either the host or the gateway verification messages wherein each verification message contains a signature which depends upon the data exchanged between the host and the gateway since the preceding verification message, the host and the gateway also called peer devices having at their disposal a same algorithm defining which of them sends a verification message at each of the predetermined instants.