NickServ allows you to "register" a nickname and prevent others from using it. ChanServ allows you to register and control various aspects of channels. ChanServ can often prevent malicious users from "taking over" channels by limiting who is allowed channel operator privileges. MemoServ is a utility allowing IRC users to send short messages to other IRC users, whether they are online at the time or not, or to channels(*). Both the sender's nickname and the target nickname or channel must be registered in order to send a memo. HostServ allows you to change your host to a virtual host of your liking. Normally only settable by and IRCop, but can be request by a user.