Usage: SECURITY AKILL ADD [<mask>] [<reason>]

This command adds a permanent autokill on the server. These are bans that will stay intact even if the server shuts down and restarts.

/as security akill add user@* Flooding the server

As with all bans, they should be carefully set to be as specific as possible while still keeping the problem user off the server. Since these bans are permanent, it is very important that you keep track of them and manually remove them when you think it appropriate.