A method for detecting the presence of fraudulent Subscriber Identity Modules in a network for cellular communications comprising the steps of: at a first Service Node, receiving a registration request by a first User Equipment comprising a Subscriber Identity Module for defining an identity of a subscriber; initiating a checking to establish whether the subscriber is already registered with the same identity in at least one Service Node over the network, including the first Service Node; if the subscriber results to be already registered with the same identity in at least a second Service Node over the network, retrieving status information on at least a second User Equipment associated with the already registered subscription for checking whether the second User Equipment is not the first User Equipment; and disabling any subscription of the subscriber associated with the identity if the second User Equipment results not to be the first User Equipment.