A method and system for monitoring users on one or more computer networks, disassociating personally identifiable information from the collected data, and storing it in a database so that the privacy of the users is protected. The system includes monitoring transactions at both a client and at a server, collecting network transaction data, and aggregating the data collected at the client and at the server. The system receives a user identifier and uses it to create an anonymized identifier. The anonymized identifier is then associated with one or more users' computer network transactions. The data is stored by a collection engine and then aggregated to a central database server across a computer network.