A system, computer implemented method, and computer storage medium encoded with a computer program, for identifying newly trending topics in a data stream. An example method includes: receiving text documents forming part of a data stream from one or more servers; identifying terms within the received text documents; deriving from the identified terms, a set of terms identified as abnormal by virtue of having a relatively high frequency of occurrence within the text documents received in a recent period compared with that expected from their historic occurrence; creating a first set of one or more clusters, each cluster including a group of terms from the set of terms identified as abnormal which through their degree of co-occurrence in the received text documents are considered to relate to the same topic; and comparing clusters of a further set with the clusters of the first set to determine whether a cluster of the further set pertains to the same topic.