Methods and systems for monitoring communication traffic in communication networks, such as Internet Protocol (IP) traffic transferred over the Internet or over a wireless network. The disclosed techniques identify communication traffic that is associated with target individuals, by extracting digital images from the traffic and recognizing target individuals who appear in the images. A correlation system monitors communication sessions that are conducted in a communication network to identify known target individuals who appear in images. Upon recognizing a target individual in an image extracted from a certain session, the system correlates this target user with one or more of the communication identifiers used in the session. The system automatically identifies IP addresses or other identifiers that are used by target individuals, and enable subsequent tracking of such identifiers.