nonsensse IM names with no responses....

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I use my yahoo IM to listen to music alot, the last few days, I've been getting messages that don't say much other than "Hi" "how have you been" and an audicon with a fish that says...."hey sexy" BUT the messages are from names like....ghegbvkygoergh jfijeifyh things that dont make much sense, they dont answer and if I bloc/spam/ignore...I get other ones anyone know what that's all about?