What was the rumors about?
I have never been the target of a Rumor because they where mostly true.
In any event. If something like that pops up consider the source and then laugh it off as the week minded fail to separate fact from fiction.
Sun has a point in that when somebody close to you (or who you view as a friend) starts a rumor you have to consider their motives and assume them to be hostile in their intents towards you.
Best give them the finger and send them on their way.