Clones are duplicate clients from the same client address. There are two general types: The first is an internet café or similar that is connecting through something like WinGate to access the web, these are valid users for your system. The second is a user that loads your server with fake clients that are usually harmful or disruptive. The default level of clone detection is set to 10 if a single host brings on more than 10 clients the server will send you an alert. To set it so that a single host can have more than 10 you use the trigger command to lift that host's threshold.
ALERT - Send notices to local or remote servers.
DETECT - Detect on local or remote servers.
LEVEL - Set the number of clones before it alerts.
OFF - Disable clone detection.
ON - Enable clone detection.
/as help security clone <topic>
Clones are a problem for two reasons. First, they take up space and resources for no particular point. Most administrators would rather their servers have a large number of people on their servers, rather than a smaller number on multiple times. The second problem is that most people load up clones with bad motivations. Some do so simply to see if they can or to experiment, but some do it to flood rooms or engage in similarly disruptive behaviors. Clones are generally not a major problem, but they should be monitored and dealt with.