A security system for a communication system that includes an IP network and groups of servers in a farm, wherein each group is associated with a customer. A user connected to the network can access information provided by a customer from a server within the group of servers associated with this customer through a dispatching device. The security system comprises setting means in each of the switches which are located between the dispatching device and the customer servers for setting a field of bits in the IP header of potentially irregular packets transmitted from a customer server and the dispatching device, means in the dispatching device for identifying any packet wherein the field of bits has been set to the predefined value, and means for deleting or logging the potentially irregular packet when the destination of the packet is not the dispatching device.