In one example, a method is described. The method includes: obtaining network traffic data including at least one user agent, where the user agent is associated with a client device coupled to a network at a media exposure measurement location, and where the user agent comprises a string of characters defining client device attributes, comparing one or more of the client device attributes to candidate device attributes stored in an audience measurement database, based on the comparison, selecting, from a set of candidate device attributes, a set of target device attributes corresponding to a target device identifier, determining a number of occurrences of the set of target device attributes in the network traffic data, and based on a determination that the number of occurrences is above a threshold, outputting the target device identifier as the device identifier that corresponds to the user agent.