Abstract: A system and a method for establishing or specifying the online status of a user forming part of an instant messaging system. The IM system includes clients having IM client applications, an IM server, and a user information database that is selectively connected to the clients via the internet. The user database stores an activity status for each user's activity with the IM server system. The activity status includes: (i) a time variable signifying the time of or time since the last prescribed involvement with the IM server; and (ii) a probability variable signifying the likelihood of the user still being online. Monitoring means is provided to continuously monitor user activity with said IM server and to continuously update the activity status of users stored on the database. Checking means is also provided to check the activity status of each user stored on the database and adjust said probability variable.