The adaptive modification of the security level of a node in a network is enabled. For example, such modification may be achieved in a dynamic network i.e. networks in which nodes may be mobile and in which the network topology is not constant. The node receives beacon signals from other nodes in the network, the signals providing an indication of the alert level of the other nodes and an indication of whether the other nodes are trusted members of the network. The alert level of the node is determined based on the received signals.