Chapter 3 Authentication for FortiOS 5.0 : Monitoring authenticated users : Monitoring IM users
  
Monitoring IM users
User lists can be managed to allow or block certain users. Each user can be assigned a policy to allow or block activity for each IM protocol. Each IM function can be individually allowed or blocked providing the administrator the granularity to block the more bandwidth consuming features such as voice chat while still allowing text messaging. The IM user monitor list displays information about instant messaging users who are currently connected. The list can be filtered by protocol. After IM users connect through the firewall, the unit displays which users are connected. You can analyze the list and decide which users to allow or block. A policy can be configured to handle unknown users.
Active IM users are viewed from User & Device > Monitor > IM.
 
IM users who are already logged on before changes are made to the IM user profile will not be affected until their next login. You cannot disconnect users who have already logged on by enabling logon blocking.
IM page
Lists all active IM users that are currently active. This page allows you to view blocked users as well as users that are currently using a particular IM protocol, such as MSN.
Protocol
Filter the list by selecting the protocol for which to display current users: AIM, ICQ, MSN, or Yahoo. All current users can also be displayed.
#
The position number of the IM user in the list.
Protocol
The protocol being used.
User Name
The name selected by the user when registering with an IM protocol. The same user name can be used for multiple IM protocols. Each user name/protocol pair appears separately in the list.
Source IP
The IP address where the user initiated the IM session from.
Last Login
The last time the current user used the protocol.
Block
Select to add the user name to the permanent black list. Each user name/protocol pair must be explicitly blocked by the administrator.