Detecting attempted intrusions in a telecommunications signaling network and assessing the vulnerability of the network to attempted intrusions. Intrusion rules are applied to received messages in the network in real-time, using a known protocol for the network, in order to detect anomalies tending to indicate an attempted intrusion. In order to assess the vulnerability of the network, vulnerability rules are applied to rankings of particular parameters relating to elements in the network. The rankings provide an indication of susceptibility of a network element to an attempted intrusion relative to other network elements.