Abstract: The present invention relates to a method and system for Internet Protocol network communications and a use thereof for protecting Internet sites against denial of service attacks on insecure public networks such as the Internet. The method utilizes a multicast address hopping technique which selectively varies the chosen multicast IP address from a set of available multicast addresses according to a predetermined scheme known to the communicating end stations but not to unauthorized end stations. The packets associated with the multicast stream are then communicated on the chosen multicast address. The set of available multicast IP addresses may also be selectively varied according to a secret predetermined scheme known to the transmitter and subscriber end stations, particularly by adding to and dropping from the set of multicast IP addresses in a seemingly random fashion.