1. A method, comprising: maintaining a list of target users of a communication network and respective speech phrases that are characteristic of the target users; selecting a plurality of candidate communication terminals from among multiple communication terminals in the communication network based on a selection criterion; analyzing speech that is communicated via the candidate communication terminals, so as to identify one or more of the speech phrases in the speech; and correlating one of the candidate communication terminals with a target user who is associated in the list with the identified speech phrases.