As instant messaging has grown in popularity, it’s also fallen prey to the same marketers that made “spam” a household word. According to Ferris Research, spim (unsolicited commercial instant messages, also called “instant spam” or “IM marketing”) doubled last year. How can you stop it? AOL IM ( http://www.aim.com ) gives you the option of only receiving messages from known contacts. ICQ ( http://www.icq.com ) goes one step further, and lets you filter out offensive words and Web links.